10 20 40 60 cm
mittakaava > 60 cm
Gösta Sundman: Suomen Kalat (Kansalliskirjasto, The National Library of Finland), Lauri Urho
- Family: Salmonids – Salmonidae
- Similar species: brown trout, chum salmon, coho salmon, pink salmon, rainbow trout
- Size: 60–110 cm, 2–12 kg, can reach 30 kg.
- Appearance: Body tapering, streamlined for speed and agility. Anal fin has max. 12 rays, which distinguishes the Atlantic salmon from the Pacific members of the family. Salmon and sea-trout (sea-going brown trout) are similar in appearance, as are the landlocked (lake) form of the salmon and the lake brown trout. However, a salmon can be distinguished from a sea-trout by the narrower ‘wrist’ to the tail, allowing it to be picked up by the tail. Also, the trailing edge of the salmon’s caudal fin is forked, while that of the sea-trout is square or even slightly convex, though this may not be clear in spawning individuals. The maxillary extends to the rear edge of the eye, while in the sea-trout it extends beyond this point. Unlike sea-trout, salmon have a single row of vomerine teeth, with no teeth on the vomerine head. Males develop a kype prior to spawning. Salmon parr, found in freshwater, bear little resemblance to adult salmon. They can be distinguished from trout parr by the more pointed tip of the long pectoral fin. Also by the maxillary, which, as in the adult, extends only to the rear edge of the eye.
- Colouring: During its feeding period in the sea the salmon’s flanks are silver, the back dark greenish to bluish. Black spots, some X-shaped, appear mainly above the lateral line, few spots on the operculum and none on the fins. Spawning adults become darker in colour, the flanks turning red or bronze. Reddish spots appear. Female lake salmon become almost black.
Salmon parr have 8-10 dark vertical bars along the flanks (‘parr marks’) with only a few red spots. Adipose fin dark grey to black.
- Reproduction: Salmon leave the sea (or lake) and ascend their native rivers to spawn in spring and summer. Spawning takes place between September and November in water 0.5 to 3 m deep and may continue for up to two weeks. Most salmon die after spawning, with only 3-6% surviving to make the return journey and spawn again. Less than 1% spawn a third time. In Finland, most salmon are the result of stocking programmes. While they ascend to the mouths of their native streams, access to the spawning grounds is often denied by dams and other constructions.
- Food: In freshwater juveniles feed on plankton and small invertebrates. In the sea salmon feed mainly on Baltic herring and sprats.
- Distribution and habitat: Present throughout the Baltic Sea and river estuaries thanks to stocking. Only two rivers currently support naturally spawning populations of Baltic Sea salmon – the Tornionjoki and Simojoki. Salmon from the Arctic Ocean spawn in the rivers Tenojoki and Näätämöjoki. A natural population of landlocked salmon is found in the Vuoksi system in SE Finland, although this too is dependent on stocking because of man-made obstructions. Salmon have also been introduced into lake Inarinjärvi in Lapland.
- Endangerment: Salmon is classified as endangered species (lake salmon critically endangered, and stands of Baltic Sea and Arctic Ocean threatened).