Habitat requirements Broad ecosystem units ES, FS, LL, LS, RE, SP, ST Critical habitats and habitat features 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. 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. 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.