The rainbow trout has many small spots scattered across its back, sides, head, and caudal fin. The back is brassy green flecked with iridescent purple and green; the venter is white or gray. A wide pink, purple, or red band marks the sides. The body form is spindle-shaped, and the mouth is terminal and large. No fins have spines. A fleshy adipose fin is present between the caudal and dorsal fins. Scales are cycloid, very small, and embedded under a thick mucus coat. Adult size 9 to 29 inches.