Life Cycle of Atlantic Salmon
The eggs (ova) begin developing right after fertilization, and depending on water temperature, will hatch in the spring.
The just-hatched fish are called alevins and still have the yolk sac containing food attached to their bodies. When most of their yolk sac has been consumed the alevins become active and begin their journey up through the gravel of the riverbed.
The fry have eight fins, that are used to maintain their position in fast flowing streams and manoeuvre about in the water. Their survival is temperature dependant and heavily influenced by predation, pollution and competition for food.
Over the autumn, the fry develop into parr with vertical stripes and spots for camouflage. They feed on aquatic insects and continue to grow for one to three years while maintaining their territory in the stream.
At a length of 12 to 24 cm (4.7 to 9.5 in.) during springtime parr transform and become smolt. A silvery sheen replaces the parr marks, and internally they undergo a complex transformation to survive in saltwater.
Grilse are salmon that reach maturity after one year at sea; these return to their river in summer weighing from 1 to 4kg. If it takes two or more years at sea to mature, the salmon will return considerably earlier in the year and larger at 3 to 15kg. These big fish are highly favoured by anglers. Salmon exhibit remarkable "homing instinct" with a very high proportion able to locate their river of origin using the earth's magnetic field, the chemical smell of their river and pheromones (chemical substances released by other salmon in the river).
Spawning In A Redd
Wild Atlantic salmon spawn in late autumn. The female digs a 10-30cm (4-12 in.) deep nest called a REDD in the gravel bottom of the stream.