Rainbow trout have small scales and a small, fleshy adipose fin on the back behind the dorsal fin. The fins lack spines. There is a small triangular projection at the base of the pelvic fin. Upper parts are dark olive, thickly speckled with black spots; the belly is silvery white. There are prominent dark spots on the tail. The side lacks orange or reddish spots, but there is a pink or reddish longitudinal stripe. The tail fin is definitely forked; the anal fin usually has 10 or 11 rays.