Coho (or silver) salmon are powerfully built, and they can jump falls that most salmon cannot negotiate. They have small black spots on their backs and the upper lobe of the tail fin. The gums at the base of the teeth are white. Although sea run coho have silver sides, spawning males develop bright red sides and greenish backs. Spawning females are paler. The jaws of spawning males often become grotesquely hooked.
Most coho spend 18 months at sea, staying in coastal waters, and they return to their home streams as 3 year olds weighing 8 to 10 pounds. The fry spend more than a year living in streams.