Trout Life Cycle
January - May
Spawning in tributaries
Trout require clean gravel and well-oxygenated water for
spawning. Rainbow trout will first spawn and 2-3 years old.
April - June
Young trout emerge from the gravel
and begin feeding.
June - September
Growth of young fish
Trout require shallow slack-water feeding areas
with vegetative or rocky cover nearby.
October - April
Over winter survival
To survive through winter, juvenile trout require cover in the
form of densely woody debris, undercut banks, and spaces
between cobbles and boulders on the stream bottom.
Winter survival is also enhanced by constant water
temperatures of 52°F found in Big Springs.
May - July
Migration from tributaries into main river
One-year-old trout (3-5 inches) migrate
downstream into Island Park Reservoir which
provides them with an abudant food source
they grow rapidly in the reservoir, attaining
lengths of 6-10 inches by age two and
reaching 16-19 inches by age three.
September - December
Migration up to tributaries
Trout 2 to 3 years and older migrate upstream
into tributaries for spawning.