California Department of Fish and Wildlife

Coho Salmon Species Characteristics

Coho salmon, (Oncorhynchus kisutch) as noted by Moyle (1976), Laufle et al. (1986), and Anderson (1995) are medium to large salmon, with spawning adults typically 40 to 70 cm (15.8 to 27.6 inches) fork length (FL) and weighing 3 to 6 kg (6.6 to 13.2 lbs). Coho salmon as large as 80 cm (31.5 inches) and 10 kg (22 lbs) have been caught in California. Identifying fin characteristics are 9 to12 major dorsal fin rays, 12 to17 anal fin rays, 13 to 16 pectoral fin rays, 9 to 11 pelvic fin rays (with an obvious axillary process at the fin base), a small fleshy adipose fin, and a slightly indented caudal fin. The scales are small and cycloid. The lateral line is complete and almost straight with 121 to 148 pored scales. Pyloric caeca number 45 to 83. There are 11 to15 branchiostegal rays on either side of the jaw. Gill rakers are rough and widely spaced, with 12 to16 on the lower limb (half) and 6 to 9 an the upper limb (half) of the first gill arch.

Spawning adults are generally dark and drab. The head and back are dark, dirty bluegreen; the sides are a dull maroon to brown with a bright red lateral streak; and the belly is gray to black (Moyle 1976; Laufle et al. 1986; Sandercock 1991). Females are paler than males, usually lacking the red streak. Characteristics of spawning males also include: hooked jaw, enlarged and more exposed teeth, slightly humped back and a more compressed head and body. The snout is less deformed than in other salmon species. Both sexes have small black spots on the back, dorsal fin, and upper lobe of the caudal fin. Except for the caudal and dorsal, the other fins lack spots. The gums of the lower jaw are grey, except the upper area at the base of the teeth, which is generally whitish.

Adult coho salmon in the ocean are steel-blue to slightly greenish on the back, silvery on the sides, and white on the belly. They have numerous small, irregular black spots on the back, upper sides above the lateral line, and base of the dorsal fin and upper lobe of the caudal fin. The adults have black mouths with white gums at the base of the teeth in the lower jaw; this is the most reliable physical feature that distinguishes them from chinook salmon (O. tshawytscha).

Juvenile coho salmon in inland waters are blue-green on the back, with silvery sides. The parr have 8 to 12 parr marks centered along the lateral line, which are more narrow than the pale interspace between them. The adipose fin is uniformly pigmented, or finely speckled giving it a grey or dusky color. The other fins lack spots and are usually orange tinted; however, the intensity of the orange tint varies greatly. The anal fin is pigmented between the rays, often producing a black and orange banding pattern. The anal fin is large, with the first few anterior rays elongated and white with black behind. The large eye and the characteristic sickle-shape of the anal and dorsal fins are characteristic of coho salmon juveniles that distinguishes them from juveniles of other Pacific salmon species.