The average length of a rainbow trout is 12-18 inches
and the steelhead is 20-30 inches. A mature steelhead usually weighs
8-9 pounds but has been known to reach 36 pounds. The body is somewhat
compressed with a rounded snout and a large mouth. The spawning
male experiences minor changes to its head, mouth and color. Stream
residents and spawners are darker with more intense coloring and
lake residents are lighter, brighter and more silvery. They range
from steel-blue, blue-green, yellow-green to almost brown. Steelhead
tend to be more silvery. All have a number of small black spots.
The coloring chamges drastically over the whole of its range.
Rainbow trout possess the well-known streamlined salmonid form,
though body shape and coloration vary widely and reflect habitat,
age, sex, and degree of maturity. The body shape may range from
slender to thick. The back may shade from blue-green to olive. There
is a reddish-pink band along each side about the midline that may
range from faint to radiant. The lower sides are usually silver,
fading to pure white beneath. Small black spots are present over
the back above the lateral line, as well as on the upper fins and
tail. In some locations, the black spots of adults may extend well
below the lateral line and even cover the entire lower side. Rainbow
trout are positively identified by the 8 to 12 rays in the anal
fin, a mouth that does not extend past the back of the eye, and
the lack of teeth at the base of the tongue. River or stream residents
normally display the most intense pink stripe coloration and heaviest
spotting followed by rainbows from lake and lake-stream systems.
Spawning trout are characterized by generally darker coloration.