Salmon are known for returning to their birthplace to spawn after migrating from freshwater to the ocean.
Many salmon species are anadromous: they hatch in rivers, migrate downstream as juveniles, grow in the sea and later return to freshwater to reproduce. This life cycle is especially associated with Pacific salmon of the genus Oncorhynchus and Atlantic salmon, Salmo salar.
Scientists believe salmon use several navigation cues, including the Earth's magnetic field during ocean travel and the distinctive chemical odor of their natal stream when they approach the coast. The exact importance of each cue varies by species and life stage.
After spawning, Pacific salmon commonly die, returning nutrients from their bodies to river and forest ecosystems. Atlantic salmon can sometimes survive spawning and reproduce again. The word salmon therefore describes a diverse group with different life histories rather than one single species.