Infographic: Atlantic salmon life cycle
Release date: February 2019
Description: Atlantic salmon life cycle
- Pea-sized orange eggs are deposited in riverbed gravel in autumn, and hatch the following early spring.
- After hatching from the egg, the salmon is called an Alevin. During this stage it remains hidden in the riverbed gravel, feeding from its attached yolk sac. It's about 2 cm in length.
- Wriggling up from the gravel, a FRY begins feeding on microscopic life in the stream. It eventually reaches a length of 5 to 8 cm before maturing into a PARR.
- Dark vertical markings, called ‘parr marks’, with a single red dot between each one, appear on the sides of young salmon (PARR). The PARR remain in the river for 1 to 6 years, depending on water temperature and food availability.
- During springtime, a silvery sheen replaces the parr marks, and the salmon undergoes an internal transformation that prepares it for life in saltwater. It begins to swim with the current rather than against it. On the downstream journey, the odours of the smolt's native river are imprinted on its memory, to be recalled when it returns to spawn.
- After one to three years, salmon return to the river in which they were born to spawn (April to November). Salmon are classified by the number of years they spend at sea; one year are GRILSE or ONE-SEA WINTER (1SW), and greater than two years are MULTI-SEA WINTER (MSW). Once in freshwater they stop feeding, living off accumulated fat reserves.
- Spawning in a redd
- In late fall, the female digs a nest, called a redd, in the gravel. She lays her eggs, then an adult male fertilizes them by releasing milt on the redd.
The female may lay 1,500 eggs for each kilogram of body weight. Atlantic salmon that return to the ocean the following spring to feed are called KELTS.
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