Spawning maturity occurs at four to seven years and they can live 12 years.
Unlike salmon, spawning adults survive to spawn again every two or three
years. They spawn in fall after the temperature drops below 48 degrees
Fahrenheit. The incubation period for their eggs is 4 to 5 months and they
hatch in late winter to early spring. They like cold, clean, undisturbed
waters. The young eat aquatic insects switching to mainly whitefish, sculpin
and other trout as they grow.
Bull Trout that live in streams rarely grow
to more than 4 pounds, but lake inhabitants can weight above 20 pounds,
with the U.S. record Bull Trout weighing in at 33 pounds.
They are known to exhibit four distinct life history forms:
- Adfluvial Bull Trout rear from one to four years in their natal stream
and then migrate to lakes, returning only to spawn.
- Fluvial Bull Trout mature in their natal streams much like their adfluvial
counterparts but move to large streams and rivers after maturation.
- Resident Bull Trout complete their entire life cycle in the tributary
(or nearby) streams in which they spawn and rear.
- Anadromous Bull Trout rear in natal streams and migrate to marine environments
to mature. This form is reported only near Puget Sound in Washington
where anadromous Bull Trout grow large in the salt water and then migrate
to mountain tributaries to spawn.
Bull Trout have a white leading edge on their fins and small, pale yellow
to crimson spots against a darker background of olive green to brown on
the back fading to white on the belly. Their tail is slightly forked and
the dorsal fin lacks spots. They look very much like the anadromous Dolly
Varden, but are larger and have a longer and broader head and exist mainly
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