JAW As the chinook begins its spawning run and prepares to fight for mates, its teeth grow and both its upper and lower jaws take on intimidating hooked shapes. To distinguish a chinook from the closely related coho salmon, examine the gums on the lower jaw: Those of a chinook will be black; a coho's will be white.
BELLY During the three to five years that the chinook is at sea, it feeds voraciously, building stores of fat to sustain it during its spawning run. Lead, mercury, and other toxins can accumulate in fatty tissue, so it is important to skin the fish and remove the strips of fat along the belly, backbone, and lateral line before cooking.
SKIN Chinook undergo many physical changes during the course of the spawning run, including the darkening of their skin from silver to near black, and the deterioration of their flesh. Salmon caught in the late phases of this color shift are the poorest fighting and foulest tasting. Target lighter and sprier fish.
FLESH Once chinooks have completed their spawning cycle, their spent bodies nourish the entire aquatic community. Rainbow trout are among the most active consumers of this resource. When you fish the spawn, be sure to bring some pale-pink "flesh flies" to cast for these salmon-fattened bruisers.