The Chinook (or king) is the largest salmon species, averaging 18 to 24 pounds with up to 127 pounds recorded. Chinook have small black spots on the back, dorsal fin, and tail fin. The gums at the base of the teeth are gray. Fall run Chinook are robust and deep bodied, while spring chinook are smaller, slimmer, and not as brightly colored when spawning.
Fall Chinook spawn soon after arriving at their spawning grounds, usually large rivers. The fry spend 3 to 4 months in fresh water. Spring chinook migrate earlier, but delay spawning until fall, and they spawn in smaller tributaries. Their fry spend a year or more in fresh water. The Sacramento River hosts a unique winter run chinook, which is now listed as endangered.