The Atlantic salmon (Salmo salar) has a complex life cycle that alternates between fresh water and salt water. This particular migration follows the species' reproduction. Here are the main stages:
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Egg: The female lays her eggs in a nest called a redd, dug in the gravel of rivers. After fertilization by the male, the eggs incubate during the winter.
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Alevin: In spring, the eggs hatch into alevins that remain hidden in the gravel, feeding on their yolk sac. Once this sac is depleted, they emerge and start feeding on microscopic organisms in the stream.
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Parr: After about a year, the young salmon develops dark vertical marks, called parr marks, separated by red spots on its flanks. It stays in the river for 1 to 6 years, depending on the water temperature and food availability.
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Smolt: In spring, the parr undergoes a transformation called smoltification, allowing it to adapt to life in salt water. Its appearance becomes silvery, and it migrates to the ocean, memorizing the scents of its native river to facilitate its future return.
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Adult at sea: At sea, the salmon grows rapidly thanks to a diet rich in crustaceans and small fish. It can cover great distances, reaching feeding areas located, for example, off the coast of Greenland or the Faroe Islands.
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Return to the river and reproduction: After 1 to 3 years at sea, the salmon returns to its original river to spawn, ceasing to feed during this period. The female digs a new redd to deposit her eggs, thus completing the life cycle.
This complex and migratory life cycle makes the Atlantic salmon particularly sensitive to environmental changes, both in fresh water and in the marine environment.
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