Illustrations of how the principal male Pacific salmon species appear when they are spawning (not proportional to actual sizes)Salmon ( //) is the common name for several species of fish in the family Salmonidae. Several other fish in the same family are called trout; the difference is often said to be that salmon migrate and trout are resident,[says who?] but this distinction does not strictly hold true. Salmon live along the coasts of both the North Atlantic (one migratory species Salmo salar) and Pacific Oceans (approximately a dozen species of the genus Oncorhynchus), and have also been introduced into the Great Lakes of North America. Salmon are intensively produced in aquaculture in many parts of the world.
Typically, salmon are anadromous: they are born in fresh water, migrate to the ocean, then return to fresh water to reproduce. However, there are populations of several species that are restricted to fresh water through their life. Folklore has it that the fish return to the exact spot where they were born to spawn; tracking studies have shown this to be true, and this homing behavior has been shown to depend on olfactory memory.