Atlantic Salmon Facts

Atlantic salmon is a species of fish that can be mainly found in the northern Atlantic ocean, as well as the rivers tributary to the north Atlantic ocean. Scientifically, it is known as Salmo salar and it is a member of the family, Salmonidae. The adult fish is known as an excellent jumper. In fact the word, 'salar' means leaper. It is not closely related to the six species of Pacific salmon. It is a distant relative of the Pacific salmon, but closely related to brown trout, which is also known as salmo trutta.

Interesting Information about Atlantic Salmon

Commercially, it is known by the names of black salmon, silver salmon, slink, bay salmon, spring salmon, winnish, kelt, grilt and landlocked salmon. It can be farmed quite easily. In fact, these fish are grown widely in United States, Canada, Norway and Chile.

Physical Appearance
It can grow up to a length of about 70 to 100 cm. An adult fish can weigh up to 2 to 10 kg, though some can grow quite large and weigh almost 30 pounds, i.e. 13.6 kg. The young fish looks quite different from the adult with the presence of blue and red spots on its body. As it matures, its body color becomes silvery blue. The most distinguishing feature of the adult Atlantic salmon is the presence of black spots above the lateral line. However, its caudal fin is not spotted, and except for the adipose fin, all other fins have black border. It possesses well-developed teeth.

Habitat and Distribution
They can be found in both freshwater rivers and oceans. They begin their life in freshwater and remain there for the first 2 to 3 years of their life. So, the young salmons live in the river where they are born, and then migrate to the ocean as they mature and undergo some physiological changes. They remain in the ocean for 2 to 3 years, after which they return to the natal river in order to spawn. They can be primarily found in Canada, Finland, Germany, France, Great Britain, Iceland, Ireland, Lithuania, Latvia, Russia, Poland, Sweden, United States, Spain, Denmark and Norway. Their major sites of reproduction are the coastal rivers of Iceland, North America, Europe and northwestern Russia.

Diet
The young salmons start hunting and feeding once their yolk sac is absorbed by the body. They primarily feed on tiny invertebrates. As they mature, they start hunting and feeding on small fish and salmon eggs. They also eat black flies, mayflies, caddisflies and stoneflies. The adult Atlantic salmon mainly feed on amphipods, capelin, crustaceans, Arctic shrimp, Arctic squid, sand eels and even herrings.

Breeding
As has been mentioned already, the coastal rivers of Iceland, Europe, North America and the northwestern Russia are their breeding grounds. The suitable spawning site for this fish is the area with coarse and loose gravel or rubble. The spawning site should have moderately strong current so that the eggs do not get smothered by silt. Usually, the female Atlantic salmon builds a nest by digging the gravel bed of a stream with the help of her tail, and lays eggs there. After laying the eggs in that depression, she covers them by shifting gravels with her tail. A female Atlantic salmon can lay about 1500 to 1800 eggs per kilogram of her body weight. The ideal time for spawning is mid October to November and the eggs usually hatch in March or April.

Life Stages
The anadromous migration pattern that this fish exhibits. The salmon eggs hatch in the month of March or April and the young salmons begin their life in freshwater. The newly hatched young salmons are called alevins. 'Alevin' is the first stage of salmon life cycle, where the fish remains in its breeding ground. In this stage, it derives nutrients from the yolk sac. Gradually, the young gills develop. When the yolk sac is completely absorbed by the body, the young salmon starts hunting, and leaves the breeding ground in search of food. This stage is called the fry stage.

The final freshwater stage of Atlantic salmon is known as 'parr'. The 'parr' develops into 'smolt' by undergoing some physiological changes, which allow it to tolerate salt water. As it attains the 'smolt' stage, it starts the journey to the ocean. During this stage, it grows quite rapidly. It spends about 2 to 4 years in the ocean and then finally reaches the 'grilse' phase. Now, it is ready to return to its natal river and during the journey, it again undergoes some physiological changes. Sense of smell is thought to help and guide this fish to return to its natal river. During this stage, the digestive system of the fish ceases to operate and hence, it can live without eating for up to 12 months before spawning. It does not die after spawning and so, can repeat the entire migration cycle again. It can live for about 15 years on an average.

Nutrition
They are not only a good source of protein, but contain a very high level of omega-3 essential fatty acids as well. It can also provide a significant amount of several vitamins and minerals like, vitamin A, vitamin B1 or thiamine, riboflavin, niacin, vitamin B6, folate, vitamin B12, vitamin D, calcium, magnesium, potassium, sodium, zinc, copper, manganese, selenium and phosphorus.

Farmed Atlantic Salmon

It is considered to be easy to farm, but this fish is very sensitive to the changes in its environment. For salmon farming, the fish are first reared in shore based freshwater hatcheries till they attain the smolt size. Later, they are placed in the floating sea cages, where they are kept for about 18 months before marketing. The excreta from large salmon farms can pollute the surrounding water, which can prove disastrous for shellfish beds. Therefore, the farmers are required to strictly monitor the condition of the surrounding water and the ecosystem. Salmon farmers are also required to reduce the amount of excreta released into the ocean, which is possible with the use of advanced technology.

Salmon can also contract bacterial, as well as fungal and viral diseases, for which farmers have to use antibiotics, vaccines and other medicines. A large part of such medications can escape into the sea water, which have raised great concern. Many people have also expressed the concern that diseases can spread from the farmed salmon to the surrounding ecosystem, which may pose a threat to wild salmon. Sometimes, farmed sea cages fail to contain the salmons, and so, some of them can escape into the surrounding water. Some such escaped salmons can reach the nearby rivers, where they can breed with wild salmon. However, efforts have been taken to reduce the accidental release of salmon with the help of efficient containment systems.

Though the 'anadromous' migration pattern is one of the most distinguishing characteristics of Atlantic salmon, many species have found to live entirely in freshwater. These are the landlocked salmon and are commonly known as ouananiche. Owning to large-scale dam construction, degradation of water quality and overfishing, the population of wild Atlantic salmon has reduced to a great extent over the years. However, several conservative efforts have been taken by various authorities to preserve its wild population.