Salmon are fishes that are noteworthy for their anadromous life cycle. They are born in fresh water, then they swim to the ocean where they live most of their lives, and then they return to fresh water to breed. Salmon are an important food fish that is heavily farmed.
Scientific & Common Names
Kingdom - Animalia
Phylum - Chordata
Class - Actinopterygii
Order - Salmoniformes
Family - Salmonidae
Genus – Salmo, Oncorhynchus
Species – S. salar, O. thsawytscha, O, keta, O. kisutch, O. masou, O. gorbuscha, O. nerka
Common Names – Atlantic Salmon, Chinook Salmon, Chum Salmon, Coho Salmon, Masu Salmon, Pink Salmon, Sockeye Salmon
Salmon are medium to large fish with a fairly long, slender body. Their coloration is usually silver or greenish, but during spawning can show varying shades of pink or deep red, depending on the species. They have hooked mouths with sharp teeth. Their second dorsal fin is what is known as an “adipose” fin – instead of the normal spines connected by a membrane between them that compose a typical fin, the adipose fin is a fleshy lump.
When salmon mature, most species embark on a journey to return to the place where they spawned. They travel upriver from the ocean, often fighting strong currents and predators such as bears. This journey can sometimes be as long as hundreds of miles.
As they become ready to mate, salmon undergo a physical change. They often become darker in color with reddish areas, and they may develop a large hump and sharper, larger teeth. Their jaws often extend and become even more hooked (this curving jaw projection is known as a “kype”).
Once they reach their destination, the salmon will spawn – females will lay their eggs which males will fertilize. Many salmon do not survive the journey, and even those who do will die soon after spawning, as the trip takes an enormous amount of effort and energy. Salmon also undergo a period of rapid deterioration due to an explosive release of hormones that prepares them to make this long and dangerous excursion to mate.
Most salmon will travel to the ocean after hatching in rivers, and spend between one and five years living there as they mature.
Salmon are what is known as a “keystone species” providing support for other important animals including bears, birds, otters and more. They provide important nutrients that are often only found in the ocean.
Some populations of salmon are completely landlocked, meaning they spend their entire lives in freshwater and never travel to the ocean and back.
The earliest known salmon appeared in the fossil record around 45 million years ago. It is believed they diverged into two separate groups – the Atlantic (Genus Salmo) and Pacific (Genus Oncorhynchus) between 10 and 20 million years ago.
Salmon are one of the most popular food fish in the world. They are both wild caught and farmed. Wild salmon face threats to their spawning habitats due to development and deforestation, and many populations have been on a declining path for over 150 years. Efforts are being made to ensure there are sustainable wild fisheries of salmon to maintain a thriving population. They also face threats from parasites, disease, climate change and overfishing.
Salmon farms can also affect other species, as they require a large amount of food to feed the farmed salmon. Salmon are predators, and farmed salmon are fed a meal that is derived from caught fish species. Too many salmon farms with too many fish can lead to lower populations of the fish used to feed the salmon, which can have a negative effect on many other species.