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Salmon is the common name for Salmonidae. Several other fish in the family are called trout; the difference is often said to be that salmon migrate and trout areresident, a distinction that holds true for the Salmo genus. Salmon live along the coasts of both the North Atlantic (one migratory species Salmo salar) and PacificOceans (approximately a dozen species of the genus Oncorhynchus), as well as having been introduced into the Great Lakes of North America.
Typically, salmon areanadromous: 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 arerestricted 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 thisto be true, and this homing behavior has been shown to depend on olfactory memory.[1][2] Salmon are intensively produced in aquaculture in many parts of the world.Salmon eggs are laid in freshwater streams typically at high latitudes. The eggs hatch into alevin or sac fry. The fry quickly develop into parr with camouflagingvertical stripes. The parr stay for 6 months to three years in their natal stream before becoming smolts, which are distinguished by their bright silvery colour withscales that are easily rubbed off. It is estimated that only 10% of all salmon eggs survive to this stage.[3] The smolt body chemistry changes, allowing them tolive in salt water. Smolts spend a portion of their out-migration time in brackish water, where their body chemistry becomes accustomed to osmoregulation in the ocean.
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