Biologically salmon are amazingly adaptable. They are born in fresh water, spend much of their lives in open sea, and then return to the river of their birth to spawn. A number of different varieties of salmon exist, with the exact classification depending largely on the oceans in which they spend most of their lives. For example, pacific salmon belong to the genus Oncorhynchus and include chinook, silver (coho), chum, pink and red (sockeye). There is only one variety of Atlantic salmon which is Salmo salar. The characteristics of salmon vary with the species, and in particular the colour of the flesh can be different. Generally the colour of the flesh of salmon range from pink through red to orange. The taste and size of the fish can also vary between the species, with chinook salmon being the largest and red salomon being the smallest. Although wild salmon is fished from the seas around Alaska, much of the commercially available fish is farmed, particularly in places such as Scotland, Canada and Norway.
Salmon has historically been an important protein food for humans. In this regard salmon is often salted or smoked in order to preserve it. As well as providing a high protein content, salmon also possesses a high concentration of long chain fatty acids of the omega-3 family including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These fatty acids are increasingly being found to benefit health because they are deficient from the typical Western diet, and addition of them to the diet corrects the naturally low levels found in most individual’s diets. Wild salmon tends to contain more fat and is therefore richer in energy, but as the fat in salmon is beneficial to the health, this can be seen as an advantage. In addition, farmed salmon has a lower protein content compared to wild salmon. Concerns over dangerous levels of toxins in farmed salmon have also been voiced. Like most seafood, salmon is also a good source of the mineral selenium, and also contains vitamin B12 and niacin.