Oncorhynchus kisutch typically spend the first year of their life in fresh water. Upon moving to the ocean, growth increases dramatically. At about the third year, coho salmon reach maturity. They weigh from 6 to 12 pounds and can be up to 38 inches in length.
Oncorhynchus kisutch are deep-bodied salmon with unique color characteristics. The dorsal surface is a metallic blue while the sides are a silver color. Black spots appear on the back and upper lobe of the caudal fin. A lateral line is also present. The line is curved toward the front of the fish and straightens out as it approaches the back of the fish. While spawning, the fish's back and belly turn dark. Spawning males' sides develop a bright red line and their jaws become hooked (Clemens and Wilby, 1961).
Range mass: 3 to 6 kg.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: sexes colored or patterned differently