Bull Trout

Salvelinus confluentus

Description

The Salvelinus confluentus (bull trout), a member of the family Salmonidae, is native to the Pacific northwest of the United States and western Canada. It was first described as Salmo spectabilis in 1856 from a specimen collected on the lower Columbia River, then subsequently described under names like Salmo confluentus and Salvelinus malma. Until 1980, bull trout and Dolly Varden (Salvelinus malma ) were considered a single species, but various kinds of evidence have been presented to demonstrate important differences between these species. Although bull trout and Dolly Varden co-occur in several northwestern Washington river drainages, there is little evidence of introgression, and the two species appear to be maintaining distinct genomes.

Bull trout and Dolly Varden look very similar. Both have small, pale-yellow to crimson spots on a darker background, which ranges from olive green to brown above, fading to white on the belly. Spawning adults develop varying amounts of red on the belly. Both species exhibit differences in size, body characteristics, coloration, and life-history behavior across their range. The elongated body is somewhat rounded with the greatest body depth below the dorsal fin. The head is long, the eyes large, the snout blunt and pointed, and the mouth terminal. Freshwater forms grow 12-18 in (30-46 cm), and the anadromous forms grow 18-24 in (46-60 cm). The color varies with size, locality, and habitat. In sea-run adults the back and upper sides are dark blue and the lower sides are silvery to white. In freshwater populations the back and upper sides are olive green to brown; the sides are a paler color. The dorsal surface and sides are marked with yellow, orange, or red spots a little smaller than the size of the eye. The paired fins and anal fin are white or creamy without spots. Spawning males, especially in anadromous populations, turn red on the ventral surface and tip of the snout. The lower jaw and parts of the head are black, and the back turns olive-brown. The spots become a more vivid orange-red, and the pectoral, pelvic, and anal fins are red-black with a white leading edge. The snout thickens and the lower jaw turns up. Females change less.

Behavior

The bull trout feeds on aquatic invertebrates, terrestrial insects that fall into its streams, and small fish. It breeds in beds of clean gravel, which are known as redds. The eggs incubate in the gravel and the larvae also live there initially. The small fish and adults live elsewhere in their stream and riverine habitat, often in pools. Some populations run to the sea, but most are landlocked and cannot do this.

Habitat

The bull trout occurs in clean, cool, freshwater rivers and streams in forested terrain. It spawns in gravel beds.

Distribution

The bull trout occurs in several geographically distinct populations, or "distinct population segments," which are isolated and do not interbreed.

The Klamath River distinct population segment (or DPS) occurs in the Klamath River. This river originates in south-central Oregon near Crater Lake National Park, flows southwest into northern California where it meets the Trinity River, and then empties into the Pacific Ocean. Bull trout in this drainage are reproductively isolated and genetically and evolutionarily distinct from those in other large rivers in the region. Bull trout were once widely distributed in the Klamath River basin, but are now limited to only seven isolated stream areas.

The Columbia River DPS occurs throughout the Columbia River basin within the United States and its tributaries (but excluding bull trout found in the Jarbidge River, Nevada; see below). Although bull trout in the upper and lower Columbia River have different lineages, no discrete geographical boundary has been established between the two groups. The Columbia River DPS is significant because the overall range of the species would be substantially reduced if this discrete population were lost. The Columbia River DPS includes bull trout residing in portions of Oregon, Washington, Idaho, and Montana. Bull trout are estimated to have once occupied about 60% of the Columbia River basin, and they presently occur in only 45% of the historical range. The Columbia River DPS is composed of 141 subpopulations. The U.S. Fish and Wildlife Service has divided the Columbia River basin area into the lower Columbia River, the mid-Columbia River, upper Columbia River, and the Snake River and its tributaries. Each division has its own set of sub-populations.

The Jarbidge River, a tributary of the Snake River located in southwest Idaho and northern Nevada, currently contains the southernmost habitat occupied by bull trout. Bull trout range in Nevada covers the East Fork Jarbidge and West Fork Jarbidge Rivers, along with Slide, Dave, Pine, and Jack Creeks. This DPS is discrete because it is segregated from other bull trout in the Snake River basin by a gap in suitable habitat of greater than 150 mi (240 km) and by several impassable dams on the main-stem Snake River.

The Coastal-Puget Sound bull trout DPS encompasses all Pacific Coast drainages within the coterminous United States north of the Columbia River in Washington, including those flowing into Puget Sound. This DPS is discrete because it is geographically segregated from other subpopulations by the Pacific Ocean and the crest of the Cascade Mountain Range. This DPS is significant to the species as a whole because it is thought to contain the only anadromous forms of bull trout in the coterminous United States, thus, occurring in a unique ecological setting.

The St. Mary-Belly River DPS is located in northwest Montana east of the Continental Divide. Both the St. Mary and Belly Rivers are tributaries of the Saskatchewan River basin in Alberta, Canada. This DPS is discrete because it is segregated from other bull trout by the Continental Divide and is the only population found east of the Continental Divide in the coterminous United States. This DPS is significant because its loss would result in a significant reduction in the range of the taxon within the coterminous United States. Bull trout in this population segment migrate across the international border with Canada.

Threats

Bull trout have been extensively displaced by introduced brook trout (Salvelinus fontinalis ), and hybrids of the two species have been verified in several streams. The brown trout (Salmo trutta ) is another introduced salmonid that is affecting some populations of bull trout. Where brook trout or brown trout co-occur with bull trout, its distribution has contracted and that of the introduced salmonids expanded. Negative effects of introduced salmonids is the most pervasive threat to bull trout subpopulations in the Columbia River basin, 62% of which are threatened by competition, predation, or displacement by non-native species. The harm caused by non-native species to the bull trout is often exacerbated by habitat conditions, water temperature, and isolation.

Many bull trout habitats have been degraded by intensive livestock grazing, mostly in lowland meadows and to a lesser extent in forested areas. Livestock grazing in the vicinity of streams and rivers promotes bank instability and erosion, and diminishes the availability of undercut banks used a trout for resting habitat. For example, of the 141 subpopulations of bull trout identified in the Columbia River DPS, about 50% are threatened by ongoing livestock grazing.

Extensive timber harvesting is another important factor degrading aquatic habitats. Activities such as clear-cutting, partial cutting with overstory removal, and selective logging for old-growth timber result in temporarily reduced riparian cover and increased water temperature. Roads built for access to timber cause increased erosion, sedimentation, and siltation of breeding habitat. For example, about 74% of the habitat in the Columbia River basin has been affected by forestry and associated roads. Latent threats of forestry are thought responsible for many of the 2,300 landslides that took place in the Clearwater and Spokane river basins during high runoff events in 1995 and 1996, which correlated closely with high logging-road density on national forest lands. These same runoff events also triggered an estimated 2,000 land slides on adjacent non-federal timber-lands in the Clearwater River basin. The effects of timber harvesting and roads on streams are long lasting, and recovery is slow. The legacy left by past forestry practices limits bull trout populations and restoration in all major watersheds. In the Wenatchee National Forest, Washington, bull trout spawning and rearing are correlated with streams not subject to past timber harvest, while in the Tucannon River Drainage timber harvesting has been responsible for the decline and isolation of bull trout in Pataha Creek.

Dams and impoundments are another important threat to bull trout, particularly on the Columbia River distinct population segment. Bull trout passage is prevented or inhibited at hydroelectric, flood-control, and irrigation dams on almost every major river in the Columbia River basin except the Salmon River in Idaho.

The direct harvesting (by fishing) of bull trout has also been an important factor in its demise, although the directed harvest has been stopped where the species is threatened. However, there is still by-catch mortality associated with recreational fishing for other trout species and salmon.

Other factors affecting bull trout in some areas include the construction and maintenance of county and state roads, the past and ongoing effects of agricultural activities, residential developments, hydro-logical diversions for irrigation, channelization, mining activities in the watershed, and pollution by sewage, nutrients, and toxic chemicals.

Conservation and Recovery

Federal, state, and local conservation and recovery actions have been undertaken to reverse the long-term declining trend for the threatened population segments of the bull trout. The actions include restrictive angling regulations, the adoption of various land-management rules, and interagency conservation programs. Federal programs that include land management plans, timber sales, and livestock grazing allotments are assessed to determine if they jeopardize the continued existence of bull trout. These actions have already begun to improve habitat conditions and reduce threats for the bull trout in some regions. Overall, however, the implementation and enforcement of existing federal and state laws designed to conserve fishery resources, maintain water quality, and protect aquatic habitat have not been sufficient to prevent the past and continuing habitat degradation that is primarily responsible for bull trout declines.

Examples of positive actions are the efforts of the Klamath Basin Working Group to: eradicate brook trout in Long, Sun and Three-Mile Creeks; reduce livestock grazing along bull trout streams; assess watershed conditions; and monitor bull trout status. Bull trout conservation in the Klamath basin has also benefited from habitat restoration activities initiated by the Upper Klamath Basin Working Group, which began in 1994. Weyerhauser Timber Company began a program of improved road maintenance in 1994 to reduce sediment inputs from roads on its lands adjacent to occupied bull trout stream reaches in the Klamath River basin, and U. S. Timberlands is continuing the practice. Timber harvests on U.S. Timberlands property occurred along Boulder Creek in 1994 and Long Creek in 1995. A review of the activities concluded that leaving buffer strips and restoring disused roads left the riparian habitat in better condition than before the timber harvest. No timber harvests are currently planned for areas adjacent to streams occupied by bull trout in the Klamath River basin. However, six of the seven bull trout subpopulations in the Klamath River basin have been affected by past forest management practices.

The bull trout in the Columbia River basin is the focus of protection efforts that will be important to its long term conservation and recovery there. However, threats continue and subpopulation improvements throughout the Columbia River have yet to be demonstrated. Chemical eradication programs were initiated in 1992 for brook trout in Sun Creek, but this also killed a number of bull trout. Ongoing management actions in Three-Mile and Long Creeks focus on brook trout eradication via selective electrofishing, snorkel-spearing, trapping, and chemical treatments with the objective of expanding bull trout range. Brook trout have declined in Three-Mile Creek, but there has been no measurable change in numbers in Long Creek.

A local Bull Trout Task Force was formed in 1994 to gather and share information on bull trout in the Jarbidge River. The task force was successful in 1997 in replacing the Jack Creek culvert with a concrete bridge to facilitate bull trout passage into Jack Creek. However, the task force has not yet developed a comprehensive conservation plan addressing all threats to bull trout in the Jarbidge River basin. The Humboldt National Forest plan was amended in 1995 to include the Inland Native Fish Strategy. This fish and wildlife habitat policy sets a no net loss objective and is currently guiding Forest Service planning of possible reconstruction of a portion of the Jarbidge Canyon Road. In June 1998, Humboldt National Forest issued the Jarbidge River Environmental Assessment for Access and Restoration between Pine Creek Campground and the Jarbidge Wilderness. Conservation actions have also been taken in support of the St. Mary-Belly River Coastal-Puget Sound bull trout DPSs.

Contacts

U.S. Fish and Wildlife Service
Snake River Basin Office
1387 S. Vinnell Way, Room 368
Boise, Idaho 83709-1657
Telephone: (208) 378-5243
Fax: (208) 378-5262

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Building
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
http://pacific.fws.gov/

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
P. O. Box 25486
Denver Federal Center
Denver, Colorado 80225
http://www.r6.fws.gov/

Reference

U.S. Fish and Wildlife Service. 1 Nov. 1999. "Endangered and Threatened Wildlife and Plants;Determination of Threatened Status for Bull Trout in the Coterminous United States; Final Rule." Federal Register 64(210):58909-58933.