Introduction to species and plant communities
This section describes the content of the accounts. Each account is organized by the following headings: status, ecology, distribution, habitat requirements, critical habitats and habitat features, and selected references. The information presented under each heading is described below.
Status refers to the provincial and national conservation status of the species or plant community.
Provincially, wildlife are ranked as either Red-listed, Blue-listed or Yellow-listed (see glossary). Yellow-listed species have been included only when designated regionally important by the Ministry of Environment, Lands and Parks (those species whose critical habitat requirements are not met by the other provisions of the Forest Practices Code such as the Biodiversity Guidebook or Riparian Management Area Guidebook).
Nationally, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC 1996) determines the status of wildlife. Wildlife designated as either ENDANGERED, THREATENED, VULNERABLE, NOT AT RISK or INDETERMINATE have been noted. (See glossary for definitions.) Where no COSEWIC designation is indicated, the species' status has not been evaluated.
A brief summary of the ecology of the species or plant community, with emphasis on biological information that may relate to the management of the species or plant community (e.g., diet, habitat use, time of breeding) is described.
The distribution is described using two ecological classification systems: the Ecoregion Classification system developed by the Ministry of Environment, Lands and Parks, and the Biogeoclimatic Ecosystem Classification system developed by the Ministry of Forests. All codes used in this section are defined in Appendix 4 and 5.
The distribution information provided represents only the current known distribution. For some species and communities our knowledge of distribution is incomplete, thus, the ecosections or biogeoclimatic units listed may not be the only ones occupied.
Maps indicate the known range, or in some cases breeding range, in B.C.
The broad ecosystem unit classification is being carried out by the Ministry of Environment, Lands and Parks. All codes used in this section are defined in Appendix 6.
Structural stages used by the Identified Wildlife are indicated here. The structural stage classification comes from the 1995 publication Standards for Terrestrial Ecosystems Mapping in British Columbia, Ecosystems Working Group of the Terrestrial Ecosystems Task Force, Resources Inventory Committee. All codes used in this section are defined in Appendix 7.
Preferred habitats or required habitat features such as wildlife trees (size, species, etc.), coarse woody debris (size, decay class, etc.), or canopy structure (height, closure, etc.), are outlined here. Codes used in the description of wildlife trees and coarse woody debris are defined in Appendix 8 and 9.
Technical information included in the account is referenced here. General references used as source material for many accounts are provided under References (page 139).
BULL TROUT (Salvelinus confluentus)
The bull trout is BLUE-listed because populations are declining throughout its global range. In B.C., the declines are mainly due to habitat degradation, disruption of migration patterns, and over fishing.
Bull trout display a variety of life-history patterns. The stream resident form is usually smaller and lives its entire life in small headwater streams where cold water and velocity barriers are common. Another form lives in large rivers and makes long spawning migrations to small tributary streams. A similar form lives as an adult in lakes and spawns in tributary streams. Both of these types often achieve large size. Migrant and resident forms can occur together. Hybrids of bull trout and dolly varden can occur in watersheds where the two species co-exist.
Lake and large river forms are often late maturing. These forms usually survive at least five summers before beginning their first spawning run. All adults do not spawn every year. Spawning migrations occur during the summer. After migrating, virtually all adults in a run congregate in a single staging area (usually a large pool), prior to spawning. Spawning occurs once water temperatures drop to about 9°C in the fall but may occur as early as mid-August. Where observed, they chose gravel sites with low to moderate velocity (0.03-0.8 m/sec), and a depth of 0.1-0.7 m in association with stream or overstream cover. Migrant forms move downstream to over winter in rivers or lakes after spawning.
The optimal incubation temperature ranges from 2-4°C. After emerging, fry disappear into the gravel along stream edges or in side channels. As they grow larger, they move to the deeper water of pools, riffles and runs. Juveniles remain near the bottom and are strongly associated with cobbles and boulders or woody debris. Optimum temperature for growth is <12°C. The diet of small fish and juveniles is mostly made up of aquatic insects taken either from the bottom or from drift. Timing of juvenile migration varies with the population and can occur any time from spring through fall. Bull trout will become piscivorous at 100-200 mm in length where other fish species are present. Sculpins, whitefish and kokanee are the preferred prey.
Bull trout likely occur in all mainland ecosections except those in the Kettle, Okanagan and Lewes river drainages. It may be absent from the Alsek river system on the north coast. It does not occur on Vancouver Island, the Queen Charlotte Islands or most coastal mainland ecosections.
South coast rivers, Fraser, Harrison, Thompson, South Thompson, North Thompson, Chilcotin, Quesnel, Stuart, Columbia, Pend Oreille, Lower Kootenay, Upper Kootenay, Kicking Horse, Illecillewaet, Nass, Kitsumkalum, Bulkley, Zymoetz, Bell-Irving, Peace, Parsnip, Finlay, Omineca, Nation, Beatton, Pine, Halfway, Liard, Fort Nelson, Kechika, Dease, Swift and Gladys drainages.
Habitat requirements
ES, FS, LL, LS, RE, SP, ST
Bull trout are extremely sensitive to habitat degradation and are considered an indicator species of ecosystem health. They appear to have a narrower range of habitat preferences than other salmonids and require clean, well-oxygenated water within a narrow range of cold temperature conditions. They may be found in high gradient areas (up to 30%) where other game fish would not be expected to occur. They are uncommon where temperatures exceed 15°C. When temperatures increase, the risk of invasion by other species that may displace bull trout increases.
The distribution and abundance of bull trout is strongly influenced by channel and hydrologic stability, substrate composition, cover, temperature and the maintenance of migration corridors. Woody debris and channel complexity may also be important. Bull trout require large, deep pools for over wintering. Increased sedimentation may lead to reduced pool depths and pool frequency, as well as reductions in interstitial spaces and channel braiding. Increased levels of sediment may reduce embryo survival, fry emergence and overwinter survival of juveniles.
Bull trout spawn in streams and tend to be extremely selective when picking a spawning site. In some systems a whole population spawns in one small area, ignoring other apparently suitable habitat. The presence of ground water may be a critical requirement. Large deep pools, often bedrock controlled, adjacent to appropriate spawning habitat may also be important. Small, very high gradient tributary streams and ground water seepage channels are often utilized for spawning and rearing. Juveniles require one to four years of stream rearing. Juveniles prefer pools and runs, up to 1.0 m in depth, with cobble and boulder substrate and overhead cover.
Access to spawning and juvenile rearing habitat is critical. Spawning habitat is often located at some distance from other seasonal habitats such as wintering or foraging habitat. It is important that migratory corridors link habitats required at different life-history stages and different seasons.
Anonymous. 1992. DRAFT Bull trout/Dolly Varden management and recovery plan. Wash. Dep. Wildl. Olympia, WA. Rep. No. 92-22.
Anonymous. 1994. A strategic plan for the conservation and management of char in
British Columbia. Large Lakes Committee. B.C. Min. Environ., Lands and Parks, Fish. Br., Victoria, B.C.
Cross, D. and L. Everest. 1994. Fish habitat attributes of entered and unentered
watersheds and the distribution of bull char spawning sites in the Upper Spokane River Ecosystem, Northern Idaho. From: the Friends of the Bull Trout Conference, Calgary, AB. May, 1994.
Dose, J.J. and B.B. Roper. 1994. Long-term changes in low-flow channel widths within
the South Umpqua watershed, Oregon. Amer. Water Resour. Assoc. Water Resour. Bull., 993-1000.
Ford, B.S., P.S. Higgins, A.F. Lewis, K.L. Cooper, T.A. Watson, C.M. Gee, G.L. Ennis
and R.L. Sweeting. 1995. Literature reviews of the life history, habitat requirements and mitigation/compensation strategies for selected fish species in the Peace, Liard and Columbia River drainages of British Columbia. Bull trout section of a report prepared for the Dep. Fish. and Oceans, Vancouver, B.C., B.C. Min. Environ., Victoria, B.C.
Gaves, S., K.L. Lillengreen, D.C. Johnson and A.T. Scholz. 1990. Fisheries habitat
evaluation on tributaries of the Coeur d'Alene Indian Reservation. Bonneville Power Administration, Portland, OR. Project No. 90-44.
Gilpin, M.E. and M.E. Soule. 1986. Minimum viable populations: processes of species
extinction. In Conservation biology: the science of scarcity and diversity. M.E. Soule (ed.). Sinauer Associates, Sunderland, MA. pp. 13-34.
Haas, G.R. and J.D. McPhail. 1991. Systematics and distributions of Dolly Varden
(Salvelinus malma) and bull trout (Salvelinus confluentus) in North America. Can. J. Fish. Sci. 48: 2191-2211.
Hemmingson, A.R. and D.V. Buchanan. 1993. Native trout project. Oreg. Dep. Fish and
Wildl. Portland, OR. Project No. F-136-R-6.
Jones, J.A. and G.E. Grant. (Draft). Peak flow responses to clearcutting and roads, western Cascades, Oregon I. Small Basins and II. Large Basins. Dep. Geosc., Oreg. State Univ., Corvalis, OR.
McPhail, J.D. and J. Baxter. 1996. A review of bull trout (Salvelinus confluentus) life
history and habitat use in the relation to compensation and improvement opportunities. B.C. Min. Environ., Lands and Parks, Victoria, B.C. Fish. Manage. Rep. No. 104.
Reiman, B.E. and J.D. McIntyre. 1993. Demographic and habitat requirements for
conservation of bull trout. U.S. Dep. Agric., For. Serv. Intermountain Res. Sta., Odgen, UT. Gen. Tech. Rep. INT-302.
