They are associated with colder water, often seeking out the coldest water in a watershed. Flow and stream channel stability are requirements for sustaining populations. Bull trout reach maturity in four to seven years and live as long as twelve years. They spawn from August to November as water temperatures drop, but spawning migration may begin in April.
Resident fish tend to be smaller and slower-growing than migratory fish.
Bull trout and Dolly Varden are closely related, but have been shown to be genetically distinct. If additional analysis is necessary the final listing decision can be delayed until December 10, 1999. This listing proposal covers all Pacific coast drainages within Washington, including Puget Sound drainages. Bull trout habitat overlaps with the range of several fish already involved in action under ESA, including Puget Sound Chinook salmon. These contribute a variety of impacts that affect bull trout throughout their various life history stages, including incubation, rearing, migration, and spawning.