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The Atlantic Salmon

Salmon Life Cycle
Illustration Courtesy of the Atlantic Salmon Trust and Robin Ade

Animal migrations represent an easily accessible source of food and are one of nature's great spectacles. The migrations of the Atlantic salmon, Salmo salar L., may cover thousands of miles from the natal river to the sub-arctic regions of the North Atlantic Ocean and precisely back; although 'landlocked' populations, that complete their life in freshwater, occur in some countries. However, the dominant life-cycle involves migration to the ocean where salmon grow rapidly on the abundant food resources available. It is because of this life-cycle that rational management requires international cooperation.

The mechanisms by which salmon navigate with such precision are not fully understood. In the ocean, the earth's magnetic field and the stars may be important. When the salmon reach coastal waters smell and taste allow precise homing to their river of birth. NASCO has established the International Atlantic Salmon Research Board (IASRB) to investigate the factors responsible for the increased mortality of salmon at sea and the opportunities to counteract them. Read more...

The Atlantic salmon, Salmo salar L. is sometimes referred to as the 'King of Fish'. Life for this regal fish begins in the gravels of rivers from Portugal, Spain and New England (USA) in the south to Ungava Bay (Canada) and Russia in the north. Spawning occurs in the autumn and winter with female salmon depositing between 1,000 - 2,000 eggs (ova) per kilogram of body weight into a nest (or redd) in the gravel. Hatching occurs the following spring and, initially, the young salmon, or alevins, are nourished by the yolk sac until they emerge from the gravel as fry to commence feeding. After the first year of life the young fish are known as parr.

migration map
Marine migrations of Atlantic salmon
Courtesy of Chad Keith, NOAA Fisherie

Following a period spent in fresh water, which is dependent on latitude and may range from one year in the south to seven years in the north, the young fish undergo an enormous behavioural and physiological change that allows them to adapt to the salty waters of the North Atlantic Ocean. These smolts migrate to the ocean in the spring and, after one or more years at sea, the adult salmon return to their natal river to complete the cycle. Most salmon die after spawning but a small proportion, mainly females, return to spawn again.

Salmon Eggs & Alevins

Salmon Eggs & Alevins

Salmon Fry

Salmon Fry
Courtesy of Panu Orell

Salmon Parr

Salmon Parr
Courtesy of Panu Orell