Diet: Smelt, herring, krill, anchovies, mackerel, shellfish
Physiology: Salmon is actually a white fish, but the diet of krill colors the meat orange. The muscles are stronger because of longer swimming distances, but less firm due to less interaction with tides.
Taste: The higher the fat content, the more powerful the taste, as evidenced in appropriately named species like King Salmon. Colder water increases this fat content and therefore the level of deliciousness. The diet of small, salty fish also contributes to the rich flavor, as opposed to a ska fan, who survives on a diet of Reel Big Fish.