I. Background Information Regarding Bull Trout

Species Status

On June 10, 1998, the U.S. Fish and Wildlife Service (Service) issued a final rule listing the Columbia River and Klamath River populations of bull trout as a threatened species (63 FR 31647) under the authority of the Endangered Species Act as amended (Act) of 1973.  The effective date of the listing was July 10, 1998. The Jarbidge River population was listed as threatened on April 8, 1999 (64 FR 17110).  On November 1, 1999, the Service listed the Coastal-Puget Sound and St. Mary-Belly River populations along with the other three populations as one “threatened” Distinct Population Segment throughout the coterminous United States (63 FR 58910), although we still refer to the five separate populations.  The Service published draft bull trout recovery plans, and a Critical Habitat Final Rule (70 FR 56211).

Species Description

Bull trout, a char in the salmonid family, were commonly known as Dolly Varden until recognized as a separate species by the American Fisheries Society in 1980.  Char are distinguished from trout and salmon by the absence of teeth in the roof of the mouth, presence of light colored spots, small scales, and differences in the structure of their skeleton.  Their spotting pattern is easily recognizable, showing pale yellow spots on the back, and pale yellow and orange or red spots on the sides. Bull trout fins are tinged with yellow or orange, while the pelvic, pectoral, and anal fins have white margins.  Bull trout have no black or dark markings on the fins. They have an elongated body covered with cycloid scales, somewhat rounded and slightly compressed laterally.  Unlike Dolly Varden, the head of a bull trout is more broad and flat on top, and hard to the touch. The bull trout was first described by Girard in 1856 from a specimen collected in the lower Columbia River.

Life History

Bull trout exhibit resident and migratory life-history strategies through much of the current range (Rieman and McIntyre 1993).  Resident bull trout complete their entire life cycle in the tributary (or nearby) streams in which they spawn and rear.  Migratory bull trout spawn in tributary streams where juvenile fish rear from one to four years before migrating to either a lake (adfluvial), a river (fluvial), or in certain coastal areas to salt water (anadromous) where they grow to maturity (Fraley and Shepard 1989; Goetz 1989).  Growth of resident fish is generally slower than migratory fish; resident fish tend to be smaller at maturity and less fecund (Fraley and Shepard 1989; Goetz 1989). The size and age of maturity for bull trout is variable depending upon life-history strategy, but they typically reach sexual maturity in 4 to 7 years. Bull trout can live as long as 12 years.

Preferred bull trout spawning habitat consists of low gradient streams with loose, clean gravel (Fraley and Shepard 1989) and water temperatures 5o to 9o C (41o to 48o F) (Goetz 1989). Spawning occurs late summer to early fall in the upper reaches of clear streams in areas of flat gradient, uniform flow, and uniform gravel or small cobble.  Bull trout typically spawn from August to November during periods of decreasing water temperatures.  However, migratory bull trout frequently begin spawning migrations as early as April, and move upstream as far as 250 kilometers (km) (155 miles (mi)) to spawning grounds (Fraley and Shepard 1989). Temperatures during spawning generally range from 4o to 10o C (39o to 51o F), with redds often constructed in stream reaches fed by springs or near other sources of cold groundwater (Goetz 1989; Pratt 1992; Rieman and McIntyre 1996).  Depending on water temperature, incubation is normally 100 to 145 days (Pratt 1992), and juveniles remain in the substrate after hatching. Time from egg deposition to emergence may surpass 200 days.  Fry normally emerge from early April through May depending upon water temperatures and increasing stream flows (Pratt 1992; Ratliff and Howell 1992). Fry and juvenile fish are strongly associated with the stream bottom and are often found at or near it.

Resident and juvenile migratory bull trout prey on terrestrial and aquatic insects, macro-zooplankton, amphipods, mysids, crayfish, and small fish (Wyman 1975; Rieman and Lukens 1979 in Rieman and McIntyre 1993; Boag 1987; Goetz 1989; Donald and Alger 1993).  Adult migratory bull trout are an apex predator that is primarily piscivorous, known to feed on various trout (Salmo spp.) and salmon (Onchorynchus spp.), whitefish (Prosopium spp.), yellow perch (Perca flavescens), and sculpin (Cottus spp.) (Fraley and Shepard 1989; Donald and Alger 1993). Growth varies depending upon life-history strategy.  Resident adults range from 150 to 300 millimeters (mm) (6 to 12 inches (in.)) total length, and migratory adults commonly reach 600 mm (24 in) or more (Pratt 1985; Goetz 1989).

Older individuals are found in deeper and faster water compared to juveniles.  Adults are often found in pools sheltered by large, organic debris or “clean” cobble substrate (McPahil and Murray 1979). Migratory bull trout may use a wide range of habitats ranging from first-to-sixth order streams and varying by season and life stage.  In intermountain areas, lower-elevation lakes and rivers constitute important habitats for maturing and overwintering fluvial and adfluvial bull trout. Resident populations are generally found in small headwater streams where they spend their entire lives. Stream resident bull trout occupy small, high-elevation streams.

Where suitable migratory corridors exist, extensive migrations are characteristic of this species. Retention and recovery of migratory life history forms and maintenance or re-establishment of stream migration corridors is considered crucial to the persistence of bull trout throughout their geographic range. Migratory bull trout facilitate the interchange of genetic material between local subpopulations and are necessary for recolonizing habitat where subpopulations are or become extirpated by natural or human-caused events.

Habitat Needs

Bull trout have habitat requirements that are more specific than those for many other salmonids (Rieman and McIntyre 1993).  Four elements relate to suitable bull trout habitat, known as the “Four C’s”: 1) CLEAN substrate composition that includes free interstitial spaces, 2) COMPLEX cover including large woody debris, undercut banks, boulders, shade, pools or deep water, 3) COLD water temperatures, and 4) CONNECTED habitats through migratory corridors.  Stream temperatures and substrate types are especially important to bull trout, with water temperature representing a critical habitat characteristic for bull trout. Temperatures above 15o C (59o F) are thought to limit bull trout distribution (Rieman and McIntyre 1993).  Spawning bull trout require hiding cover such as logs and undercut banks. Strict habitat requirements make spawning and incubation habitat for bull trout limited and valuable (Fraley and Shepard 1989).  Strong populations require high stream channel complexity, and are likely to be found in areas with low road densities, on forested lands, and in mid-size streams at relatively high elevations (> 5000 feet) (Quigley and Arbeldide 1997). However, because bull trout exhibit a patchy distribution, even in undisturbed habitats (Rieman and McIntyre 1993), fish are not likely to simultaneously occupy all available habitats (Rieman et al. 1997).

Threats

Bull trout are vulnerable to many of the same threats that have reduced salmon populations in the Columbia River Basin.  They are more sensitive to increased water temperatures, poor water quality, and low flow conditions than many other salmonids.  Past and continuing land management activities such as timber harvest, livestock grazing, road construction, and mining have degraded stream habitat, especially those along larger river systems and stream areas located in valley bottoms, to the point where bull trout can no longer survive or successfully reproduce. Cumulative impacts of these activities are increased stream temperatures, more fine sediment in spawning gravels, loss of stream channel stability, and the creation of migration barriers. Road construction and maintenance account for a majority of man-induced sediment loads to streams in forested areas (Shepard et al. 1984; Cederholm and Reid 1987; Furniss et al. 1991). Sedimentation affects streams by reducing pool depth, altering substrate composition, reducing interstitial space, and causing braiding of channels (Rieman and McIntyre 1993), which reduce carrying capacity. Sedimentation negatively affects bull trout embryo survival and juvenile bull trout rearing densities (Shepard et al. 1984; Pratt 1992).

Large dams built for flood control and power production have eliminated riverine habitat and restricted bull trout movement.  Culverts installed at road crossings may also act as barriers to bull trout movement.  Additionally, irrigation withdrawls including diversions can dewater spawning and rearing streams, impede fish passage and migration, and cause entrainment. Discharging pollutants such as nutrients, agricultural chemicals, animal waste, and sediment into spawning and rearing waters is also detrimental.  The loss and degradation of habitat has isolated many populations, increasing the risk of extinction due to demographic, genetic, and environmental stochasticity, and other natural catastrophic events.  In many watersheds, remaining bull trout are small, resident fish isolated in headwater streams.

Historically, both intentional reductions and liberal harvest regulations posed a threat to some bull trout populations. Bull trout can no longer be legally harvested in Idaho, but misidentification of bull trout as brook trout or lake trout is resulting in some fish being killed accidentally. Illegal poaching of spawning adults is a problem in some areas.

Hybridization, competition, and predation from non-native species has also been detrimental to bull trout. Brook trout readily spawn with bull trout creating a hybrid that is often sterile. Lake trout have out-competed and replaced adfluvial populations of bull trout in some lakes.  Overall, interspecific interactions, including predation, with non-native species may exacerbate stresses on bull trout from habitat degradation, fragmentation, isolation, and species interactions (Rieman and McIntyre 1993).

Warmer temperature regimes associated with global climate change represent another risk factor for bull trout.  Increased stream temperature is a recognized effect of a warming climate (ISAB 2007).  Species at the southern margin of their range that are associated with colder water temperatures, such as the bull trout, are likely to become restricted to smaller more disjunct habitat patches or become extirpated as the climate warms (Rieman et al. 2007).  Climate warming is projected to result in the loss of 22 to 92 percent of suitable bull trout habitat in the Columbia River basin (ISAB 2007).  Habitat conservation and restoration will be needed to mitigate these habitat losses.

References

Cederholm, C.J., and L.M. Reid. 1987. Impact of forest management on coho salmon (Oncorhynchus kisutch) populations of the Clearwater River, Washington: a project summary.

Salo, E.O., and W.C. Terrance, eds. Streamside managenment: forestry and fishery interactions. Pages 373-398. College of Forest Resources, University of Washington, Seattle.

Donald, D.B.; Alger, D.J. 1992. Geographic distribution, species displacement, and niche
Overlap or lake trout and bull trout in mountain lakes.  Canadian Journal of Zoology. 71:238-247.

Federal Register Notice (61 FR 4722): February 7, 1996.

Federal Register Notice (63 FR 31647): June 10, 1998.

Federal Register Notice (64 FR 17110): April 8, 1999.

Federal Register Notice (64 FR 58910): November 1, 1999.

Federal Register Notice (70 FR 56211), September 26, 2005.

Fraley, J. J. and B. B. Shepard.  1989. Life History, Ecology, and Population Status of Migratory Bull Trout (Salvelinus confluentus) in the Flathead Lake River System, Montana.  Northwest Science 63(4);133-143.

Furniss, M.J., T.D. Roelofs, and C.S. Yee. 1991. Road Construction and Maitenance.  Chapter 8 in Influences of Forest and Rangeland Management on Salmonid Fishes and Their Habitats.  American Fisheries Society Special Publication 19:297-323.

Goetz, F. 1989. Biology of the bull trout, Salvelinus confluentus, a literature review.  Eugene, OR U.S. Department of Agriculture, Forest Service, Willamette National Forest.  53 p. :

Howell, P.J.; Buchanan, D.B., eds. 1992. Proceedings of the Gearhart Mountain bull trout workshop.; 1992 August; Gearhart Mountain, OR. Corvallis, OR: Oregon Chapter of the American Fisheries Society.  67 p.

Independent Scientific Advisory Board (ISAB).  2007.  Climate Change Impacts on Columbia River Fish and Wildlife.  Available online: http://www.nwcouncil.org/library/isab/isa2oo7-2.htm.

Johnson and Weller 1994 in 63 FR 31647

McPhail, J. D. and C. B. Murray. 1979. The Early Life-history and Ecology of Dolly Varden (Salvelinus malma) in the upper Arrow Lakes. University of British Columbia, Department of Zoology and Institute of Animal Resources, Vancouver, B.C.

Pratt, K.L. 1985. Pend Oreille trout and char life history study.  Boise, ID: Idaho Department of Fish and Game. 105 p.

Pratt, K.L. 1992. A review of bull trout life history. In: Howell, P.J.; Buchanan, D.B., eds. Proceedings of the Gearhart Mountain bull trout workshop.; 1992 August; Gearhart Mountain, OR.  Corvallis, OR: Oregon Chapter of the American Fisheries Society:  5-9.

Quigley and Arbelbide 1997 in 63 FR 31647

Ratcliff, D.E.; Howell, P.J. 1992.  The status of bull trout populations in Oregon.  In: Howell, P.J.; Buchanan, D.B., eds. Proceedings of the Gearhart Mountain bull trout workshop.; 1992 August; Gearhart Mountain, OR. Corvallis, OR: Oregon Chapter of the American Fisheries Society.  10­17 p
 

Rieman, B.E., S. Adams, D. Horan, D. Nagel, and C. Luce.  In press.  Anticipated climate warming effects on bull trout habitats and populations     across the Interior Columbia River Basin.  Transactions of the American Fisheries Society

Reiman, B. E. and J. D. McIntyre.  1993. Demographic and Habitat Requirements for Conservation of Bull Trout.  Gen. Tech. Rep. INT-302.  Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station, Boise, ID.  38p

Rieman, B.E.; Lukens, J.R. 1979. Lake and reservoir investigations: Priest Lake creel census.  Job Completion Rep., Proj. F-73-R-1, Subproj. III, Study I, Job I.  Boise, ID.  Idaho Department of Fish and Game.  105 p.

Shepard, B., S.A. Leathe, T.M. Weaver, and M.D. Enk. 1984. Monitoring levels of fine sediment within tributaries to Flathead Lake, and impacts of fine sediment on bull trout recruitment.  Unpublished paper presented at the Wild Trout III Symposium.  Yellowstone National Park, WY.  On file at: Montana Department of Fish, Wildlife and Parks, Kalispell, MT.

U.S. Fish and Wildlife Service.  2002. Chapter one of the draft recovery plan for bull trout .

II. Guidelines for Analyzing Effects of Actions on Bull Trout and Their Habitat

A biological assessment is required if bull trout or bull trout critical habitat may be present in the action area of major construction activities proposed or funded by Federal agencies.  One of the purposes of the biological assessment is to help make the determination of whether the proposed action is likely to adversely affect bull trout or critical habitat. To make such a determination, a biological assessment must describe and analyze the direct, indirect, and cumulative effects of each federal action, and determine the degree of effects to bull trout.  When critical habitat is proposed, the biological assessment must also address effects on proposed critical habitat and determine the degree of effect on proposed critical habitat.  Analysis of effects must also assess the indirect effects resulting from interdependent and interrelated federal and non-federal actions.

In 1998, the Service developed a document titled “A Framework to Assist in Making Endangered Species Act Determinations of Effect for Individual or Grouped Actions at the Bull Trout Subpopulation Watershed Scale”.  It was designed to facilitate and standardize determinations of effect for Endangered Species Act (ESA) consultations focusing on bull trout. Bull trout, especially with their migratory habits, use or depend on entire watersheds to complete their life cycle. Bull trout biology and cumulative effects  must be analyzed in a watershed context in order to account for baseline conditions, to predict impacts from future actions, and to assess the complete life cycle of bull trout. This framework is best applied to individual or grouped actions at the 5th field Hydrologic Unit Code (HUC) watershed scale. This framework document contains definitions of ESA effects and examples of effects determinations, a recommended reading list to help in understanding the importance of an indicator on bull trout, a matrix of diagnostics/pathways of effects and indicators of those effects, a checklist for documenting the environmental baseline and effects of the proposed action(s) on the relevant indicators, and a dichotomous key for making determinations of effect.  We have included the matrix, the check list, and the dichotomous key to assist you in making your effects determinations.