Wild salmon
In nature, there are different species of salmon. This kind of fish attracts a lot of attention from researchers. We will follow the Atlantic salmon to understand how it lives and reproduces in fresh water. We will then understand why it leaves its native river to go to marine waters before returning to its source.
Types of salmon:
The name Salmon is a vernacular word for fish that belong to the family Salmonidae. There are over 60 species worldwide. Salmon of the genus Salmo are identified as the Atlantic salmon named Salmo salar. The Salmo salar has a large head, its body has a spindle shape. It is covered with small scales. This kind of salmon reaches a weight of more than 35 kg, but its length does not exceed 150 cm.
Another genus that exists is the Oncorhynchus which contains: King salmon, silver salmon, Pacific salmon, Japanese salmon, pink salmon.
Name of salmon according to its age and life stages:
Salmon are referred to by different terms depending on their age and life stages. Until the age of 6 weeks, it is called Fry. When it measures about 15 cm, the equivalent of the first two or three years of the salmon's life, it is called Parr.
Smolt is the name given to the salmon when it starts to migrate. Its body is tapered, its livery is silvery, and its eyes are larger. This physical metamorphosis of the salmon is called smoltification.
The unibermarin is the summer salmon, its weight is between 2 and 4 kg. Its length is about 70 cm. At this stage, the salmon has spent one year at sea.
Concerning the salmon that have spent 2 years at sea, they are called Dibermarins. A Dibermarin measures between 70 and 90 cm and weighs between 4 and 4,5 kg.
Then, the salmon that have spent 3 years at sea are called Tribermarins. The Tribermarin has a length that exceeds 90 cm and a weight of at least 8 kg.
Finally, the salmon that seeks to return to reproduce and has a variable weight is called Redibermarin. After its migration, which may have lasted several years, it seeks to return to its native river.
the salmon's life cycle :
Salmon swim up a river to reproduce. They are anadromous. The salmon is a fish that has a particular life cycle. It lives in two different and even contradictory environments. It is marine water and freshwater. So it is an amphidromous fish.
Salmon swim up rivers to spawn in their place of origin and then leave marine waters.
During the fall, adult salmon prepare aquatic sites where female salmon lay their eggs. These are spawning grounds built in rivers on fine gravel. These spawning grounds benefit from oxygenation with the help of the fast and regular currents found in the rivers. The salmon stay in this area all winter until they hatch in March and April.
The newly born fry are protected deep in the gravel so that they are not swept away. They emerge from their spawning grounds in May and begin to eat small insect larvae.
Salmon spend their first three years of life at most without leaving their native river, especially Atlantic salmon. After that, they migrate to the ocean, to the cold waters more precisely, and stay for a period of one to three years. They are found in Norway, Greenland and the Faroe Islands. This period is characterized by its considerable development because during each year spent in cold waters its weight is doubled.
When the breeding season of the salmon arrives, the spawning, begins the downstream. The migratory salmon descends, during the summer, a river and returns to its native river, its place of reproduction that is called Homing. During this run, the salmon do not feed. This migratory fish goes to great lengths to reach the spawning grounds. It is an exhausting migration where many salmon lose their lives. A salmon has the power to withstand several spawns. They return to the marine environment once they have finished spawning, only to return a year to three years later and then leave again.