The Atlantic Salmon Life Cycle
The Atlantic salmon life cycle is a complex one. Salmon are of the family Salmonidae. They share this family with trout, but they differ essentially from trout through their migratory habits. Trout have a stronger residential nature. Salmon are anadromous marine animals. This means that they start off life in the fresh waters of a river, usually a shallow tributary of a larger river. They make their way down to the sea from their river home by the time they have grown to smolts, which takes one to three years usually.
The smolts migrate north from the UK to cooler waters where the feeding is better. This can be the relatively short distance to the Faroe islands, or the much longer distance to the Davis Straits between Greenland and Canada. The salmon stay in the northern water for around two or three years before migrating back to the river stream or tributary where they were born to spawn and start a new generation of salmon. Tracking tests performed on the Atlantic salmon life cycle have shown that salmon really do return to the exact spot where they started life, but how exactly this mechanism works is still unknown.
It is in late autumn that the female salmon buries her fertilised eggs in as kind of nest she "digs" out with her tail, known as a redd. She makes the redd in the stream gravel, deposits the eggs, then makes another redd slightly further upstream, which has the effect of covering up and burying the first redd.
In late spring the new generation of salmon hatch out. Around four weeks or so after hatching, the alevins emerge from the gravel to seek out food. At this stage of the Atlantic salmon life cycle the fish are known as fry. The fry are very small, but they very rapidly become parr. At this stage they have camouflaged vertical side markings. The parr are not very much larger than fry. They start at about two inches long. They feed in the fresh water for around three years, sometimes less, before becoming smolts. At this stage they are ready to make the long journey down to the ocean.
Smolts no longer have the vertical markings of the parr. They are around six inches long and silvery in appearance. Weighing in at around two ounces, these little fish start their epic journey in late spring or early summer. The smolts head north once they reach the Atlantic. Some head for the Faroe islands, or further north to northern Norway to feed. The ones who really travel are those who cross the Atlantic to arrive in the colder waters between Greenland and Canada.
Some of the salmon will reach maturity in about one year. Others will take three years or more. Once mature the salmon will begin the reverse journey back to where they started out from. They will arrive back in the river the were born in and spawn. Because of the incredible efforts needed for such a journey, many fish die at this point. However, there are plenty of instances in the Atlantic salmon life cycle where fish have migrated and spawned two or even three times successfully.
