Freshwater Coho Silver Salmon original artwork of fish in freshwater / spawning phase of their life. Nature, wildlife, fisherman & chefs will enjoy our original fish series of steelhead & salmon. Prints & gifts. The Coho salmon, Oncorhynchus kisutch, is a species of anadromous fish in the salmon family. Coho salmon are also known as silver salmon or "silvers". During their ocean phase, Coho have silver sides and dark blue backs. During their spawning phase, the jaws and teeth of the coho become hooked, and they develop bright red sides, bluish green heads and backs, dark bellies with dark spots on their back. Sexually maturing coho develop a light pink or rose shading along the belly and the males may show a slight arching of the back. Mature coho salmon have a pronounced red skin color with darker backs and average 28 inches in length and seven to 11 pounds in weight, although coho weighing up to 36 pounds have been reported. Mature females may be darker than males, with both showing a pronounced hook on the nose.