The diagram shows the different stages in the life cycle of a salmon.
Overall, the cycle takes almost ten years and comprises three main stages, each of which takes place in a different aquatic environment.
The salmon begins life as an egg, in the slow-moving waters of the upper river, sheltered by reeds and small stones. Over a period of five to six months, the eggs hatch into very small fish known as ‘fry’, which can grow up to eight centimetres in length. The fry then move to the faster flowing water of the lower river, where they remain for a period of four years and continue to grow. During this phase, they can double or triple in size, reaching 12 to 15 centimetres, and are now referred to as ‘smolt’.
At the end of this stage, the smolt leave the river for the open seohare they will spend the next five years of their life. It is in this salt-water environment that the fish develops its characteristic shape and colouring and reaches its full length of 70 to 76 centimetres, almost ten times its original size. Finally, the adult salmon will return to the slow-moving river to lay its eggs, and the cycle will begin again.