Silver, hooknose, sea trout, and blueback (young only).
Coho salmon have black spotting confined to the back and upper lobe of the caudal fin (which in most cases is absent). Also, there is the absence of black pigment along the base of the teeth in the lower jaw, however the tongue is black, teeth are needle-like and firmly set, and the 19-25 rough gill rakers are widely spaced.
Pre-spawning adults are metallic blue on the dorsal surface, silvery on sides, ventral surface, and the caudal peduncle. Irregular black spots on the back and upper lobe of the caudal fin. The flesh along the base of the teeth on the lower jaw is pale. Flesh colour is pink to red.
At spawning time the maturing males in freshwater exhibit a brilliant red stripe on the sides, bright green on the back and head, often dark on the belly. Females are less strongly coloured, usually bronze to pinkish red on the sides.
The body is typically troutlike, elongated, depth about 4.1 into standard length, deepest behind the tips of the pectoral fins, and moderately compressed. Head length is about 3.4 into standard length. Mouth is terminal, large, and slightly oblique. The upper jaw extends beyond the posterior margin of the orbit. Snout is narrowly rounded (the upper jaw is strongly hooked in spawning males). Lips are fleshy. They have well developed teeth in both jaws, on the head and shaft of vomer, on the palatines, and tongue, however there are no teeth on the basibranchials.
The interorbital space is high, wide, rounded, its width about 3 into head length. Eye diameter is about 6.3 into head length. Gill membranes are free of each other and of the isthmus. The first gill arch has from 18 to 25 rough and widely spaced gill rakers. The caudal peduncle is compressed, relatively deep, and its least depth is about 11 into standard length. Pyloric caeca range from 45 to 83. Scales are cycloid with 118 to 147 scales above the lateral line, and 121 to 140 on the lateral line.
Adipose fin is small, slender, and fleshy. The number of rays in each of the fins are: dorsal, 9-13; anal, 13-16; pectorals, about 15; and, pelvics, about 11 (abdominal, each with a free tipped fleshy appendage above its insertion). The caudal fin is slightly indented.
In spawning males the upper jaw forms an elongated hooked snout, and the teeth are enlarged. The female’s jaw development is less extreme, except in very large females.