Bull Trout

In late August through September, spawning Bull Trout seek out the cold water refuge of the upper Lostine River watershed to construct their redds and spawn. As summer water temperatures increase, they continually seek colder water higher in watershed. They are an important indicator species relative to climate change as their sensitivity to increasing water temperatures puts them at risk. Protecting freshwater habitat is crucial to the survival of native Bull Trout and many other species that depend on cold water habitats to complete their life cycle.

Many trout species will "hybridize" including Brook Trout and Bull Trout. Spawn timing for both species overlaps in late August and September, however other environmental factors are likely driving the incidence of hybridization, rather than their proximity and similar reproductive timing. In some systems, degraded stream conditions have greatly 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. A simple key is listed below to help identify the differences for Brook Trout, Bull Trout and Hybrids:

• Brook Trout: The dorsal fin has solid black markings with distinct edges
• Bull Trout: The dorsal fin lacks light or dark markings. Some fish may have a few light markings along the base of the dorsal fin
• Hybrids: The dorsal fin may have light or dark markings, but they lack distinct edges