Chinook salmon and king salmon are actually the same species of fish. Chinook salmon (Oncorhynchus tshawytscha) is commonly referred to as king salmon in the United States, particularly in the Pacific Northwest. The name "king salmon" is derived from their large size and is used to distinguish them from other salmon species such as coho, sockeye, and pink salmon. So, Chinook salmon and king salmon refer to the same fish species.