Salmon is the common name for several species of fish in the family Salmonidae.
They are native to tributaries of the North Atlantic and Pacific Ocean.
There are seven species of Pacific salmon. Five of them occur in North American waters: chinook, coho, chum, sockeye, and pink. Masu and amago salmon occur only in Asia. There is one species of Atlantic salmon.
Chinook/king salmon are the largest salmon and range in size from 61 to 91 centimeters (24 to 36 in), but may be up to 1.5 meters (58 in) in length; they average 4.5 to 22.7 kg (10 to 50 lb), but may reach 59 kg (130 lb).
Pink salmon are the smallest at up to 76 cm (30 inches) long and 5.4 kg (12 lb), although they average 1.3 to 2.3 kg (3 to 5 lb).
Salmon appearance varies greatly from species to species. They can be silvery, greenish covered with black spots or/and stripes.
Typically, salmon are anadromous, meaning they hatch in fresh water, migrate to the ocean, then return to fresh water to reproduce. The journey made by those salmon that survive this quest to reproduce is one of nature’s greatest triumphs.
The salmon must swim hundreds miles, to get back to the stream where they hatched. Whilst many simply do not have enough fat stores to make the trip, others must battle through fishermen’s nets, over power dams, up waterfalls and rapids, and struggle past eagles, otters and bears to reach their destination.
Salmons change the color of the body on their way from the ocean to the freshwater habitats during the mating season. They may also grow a hump, develop canine-like teeth, or develop a kype (a pronounced curvature of the jaws in male salmon).
Salmon spend between 1 and 7 years out in the ocean, depending on the species.
They come back to the stream where they were ‘born’ because they ‘know’ it is a good place to spawn; they won’t waste time looking for a stream with good habitat and other salmon.
Scientists believe that salmon navigate by using the Earth’s magnetic field like a compass. When they find the river they came from, they start using smell to find their way back to their home stream. They build their ‘smell memory-bank’ when they start migrating to the ocean as young fish.
They use all their energy for returning to their home stream, for making eggs, and digging the nest. Most of them stop eating when they return to freshwater and have no energy left for a return trip to the ocean after spawning. After they die, other animals eat them (but people don’t) or they decompose, adding nutrients to the stream.
Unlike Pacific salmon, Atlantic salmon do not die after spawning, so adults can repeat the migration and spawning pattern several times, although most spawn only once or twice.
To lay her roe, the female salmon uses her tail, to create a low-pressure zone, lifting gravel to be swept downstream, excavating a shallow depression, called a redd. The redd may sometimes contain 5,000 eggs covering 2.8 square meters (30 sq ft). [Photo below: Eggs in different stages of development]
Salmon eggs are laid in freshwater streams typically at high latitudes. The eggs hatch into alevin or sac fry. The fry quickly develop into parr with camouflaging vertical stripes. The parr stay for six months to three years in their natal stream before becoming smolts. Only 10% of all salmon eggs are estimated to survive to this stage. The smolt body chemistry changes, allowing them to live in salt water.
Young salmon feed on terrestrial and aquatic insects, amphipods, and other crustaceans while young; adults eat primarily other fish and also squid, eels, and shrimp. Unlike all other salmon, the sockeye salmon has a diet that consists almost entirely of plankton.
There are diverse predators of salmon at the varying stages of their lives. Other fish, members of their own species, snakes and birds eat salmon fry. Once in the ocean, salmon are prey to whales, dolphins, seals, sea lions, other fish and, of course, humans. Bears and birds often scoop up spawning salmon.
Many species of salmon have been introduced into non-native environments such as the Great Lakes of North America and Patagonia in South America.
Salmon are intensively farmed in many parts of the world. It is a major contributor to the world production of farmed finfish, representing about US$10 billion annually. [Photo below: Salmon Farm]
A variant method of fish stocking, called ocean ranching, is under development in Alaska. There, the young salmon are released into the ocean far from any wild salmon streams. When it is time for them to spawn, they return to where they were released, where fishermen can catch them.
Salmon is a popular food. Classified as an oily fish, salmon is considered to be healthy due to the fish’s high protein, high omega-3 fatty acids, and high vitamin D.
Smoked salmon is a preparation of salmon, typically a fillet that has been cured and hot or cold smoked. Due to its moderately high price, smoked salmon is considered a delicacy.
The salmon has long been at the heart of the culture and livelihood of coastal dwellers, which can be traced as far back as 5,000 years when archeologists discovered Nisqually tribes remnants.
Salmon are central spiritually and culturally to Native American mythology on the Pacific coast, from the Haida and Coast Salish peoples, to the Nuu-chah-nulth peoples in British Columbia.
The salmon is an important creature in several strands of Celtic mythology and poetry, which often associated them with wisdom and venerability.
In Irish mythology, a creature called the Salmon of Knowledge plays key role in the tale The Boyhood Deeds of Fionn.
Salmon also feature in Welsh mythology. In the prose tale Culhwch and Olwen, the Salmon of Llyn Llyw is the oldest animal in Britain, and the only creature who knows the location of Mabon ap Modron.
In Norse mythology, after Loki tricked the blind god Höðr into killing his brother Baldr, Loki jumped into a river and transformed himself into a salmon to escape punishment from the other gods.