Diagnosis: Body elongate, somewhat compressed especially in larger fish. No nuptial tubercles but minor changes to head, mouth and color occur especially in spawning males. Colouration varies with habitat, size, and sexual condition; stream residents and spawners darker, colours more intense; lake residents lighter, brighter, and more silvery. Caudal fin with 19 rays (Ref. 2196). Differs from Oncorhynchus gorbuscha by having the following unique characters: anal fin with 6-9½ (usually 8½ ) branched rays; 115-130 scales in midlateral row; 16-17 gill rakers; breeding males lacking hump; juveniles lacking parr marks; wide pink to red stripe from head to caudal base, except in sea-run form; and juveniles with 5-10 parr marks (Ref. 59043).

Description: Streamlined body with very small scales (Ref. 52193). Head rounded; mouth terminal, extending to hind margin of orbit when closed; jaws with sharp teeth, lower jaws of mature males slightly enlarged and hooked (Ref. 52193). Dorsal fin with 4 unbranched and 10-12 branched rays; anal fin with 3 unbranched and 6-12 branched rays; dorsal fin in midbody; small lobate adipose fin; caudal fin shallowly forked (Ref. 52193, 59043).

Colouration: Colouration distinctive, body silvery or light golden with small black spots; dorsal and caudal fins black spotted; adipose fin with black edge and spotes; a broad lilac-mauve iridescent band from head to caudal fin (Ref. 52193). Older males tend to darken; juveniles have about 10 broad dark grey vertical bars along the body (Ref. 52193).