Atlantic Salmon

Distinguished from congeners by having the following unique characters: 10-13 scales between end of adipose base and lateral line; 17-24 gill rakers (Ref. 59043); caudal fin deeply forked in individuals smaller than 20 cm SL; hyaline or grey adipose margin; posterior part of vomer toothless (Ref. 59043). Mouth extends only to area below rear of eye and has well developed teeth (Ref. 51442). Vomerine teeth weak (Ref. 7251). Caudal fin with 19 rays (Ref. 2196). Little scales (Ref. 51442). Juveniles have 8-12 blue-violet spots on the flanks with little red spots in-between (Ref. 51442). Adults at sea are bluish-green dorsally becoming silvery along the sides and white ventrally; with a few black spots but none under lateral line (Ref. 37032, Ref. 51442). Caudal fin usually unspotted and adipose fin not black bordered. During reproduction individuals lose the silvery shine and become dull brown or yellowish. Males may be mottled with red or have large black patches (Refs. 37032, 51442, 88171). Skin becomes thick and leathery. Survivors lose their spawning coloration and are generally dark in colour (Ref. 84357). During the spawning season, males are characterized by elongated hooked jaws that meet at the tips, thicker fins, and slime covering their body. Hook of males dwindle after spawning (Ref. 35388).

Enteric Redmouth Disease. Bacterial diseases

Epitheliocystis. Bacterial diseases

Edwardsiellosis. Bacterial diseases

At the onset of sexual maturity this species is known to return from the ocean to the river where it was born, and even to its specific natal site (Refs. 7471, 51442). Lacustrine populations move to tributaries (Ref. 59043). Spawning migration into freshwater lasts from June to November. Spawns at 6-10°C (Ref. 89464) in gravel river areas far upstream with moderate to fast-flowing, well-oxygenated waters and a succession of riffles and pools (Refs. 6390, 59043). The female selects a site where the gravel is of the right size and of sufficient depth (0.1 to 0.3 m) (Refs. 7471, 51442) and water depth is around 0.5-3 m (Ref. 35387). The female digs a depression ("redd") by turning on her side and flexing her body up and down, without touching the stones (Ref. 36794). This species spawns in pairs. The male guards and defends the female against other males (Ref. 59043). A female releases between 8,000-25,000 eggs during a spawning season (Ref. 7471, 88187); 500 to 2000 per kg (Ref. 51442). Fertilized eggs sink into the redd and are covered with a layer of gravel (0.1-0.3 m) usually by the male (Refs. 7471, 59043). Females are also observed to cover the eggs. Individual spawning is completed in 2-3 days (Ref. 7471) after a female digging several redds and spawning with several males. Period of spawning lasts for 1-2 weeks. Most males die after spawning, while 10-40% of females may survive and return to the sea in autumn or overwinter in rivers, feed one summer, and migrate again. They may spawn in the year following the first reproduction or may remain at sea for 18 months before returning once more to the river. Of the returning females, about 0.3-6 % spawn a second time and very few spawn a third or fourth time. In short rivers with presumably less exhaustive upstream migration, up to 34% of returning individuals spawn a second time; some individuals may spawn for up to six seasons (Ref. 59043). Eggs hatch in spring, usually after 70-160 days (Ref. 59043). Upon hatching, alevins (i.e. newly-hatched young up to 1 month) are negatively phototactic and move deeper into the gravel (Refs. 58137, 59043). As their yolk sac is absorbed, the fry emerge from the bottom and move to shallow riffles just downstream of their redd (Ref. 59043). Mortality of young individuals during the first months may range from 14-61 % (Ref. 89465). Parr (i.e. juveniles) may remain in freshwater environments for 1-7 years (depending on temperature and feeding conditions) but most stay for 2-3 years. Parr undergo morphological and physiological changes called smoltification which prepares them for life in the sea. At the southern end of their range, many reach a length of 12-15 cm, transform into smolts and are ready for migration in spring of the first year after hatching (Refs. 7471, 51442). At the northern end of the range they may take 5-6 years to reach smolt stage (Ref. 36794). Smolts move towards estuaries, the continental shelf and eventually the open ocean (Ref. 89462). The Atlantic salmon matures between 3-7 years (Ref. 41851). After 1-4 years at sea, it migrates back to the upper reaches of its natal river to spawn (Refs. 59043, 89461). It has an acute sense of smell and it is suggested that it imprints a sequence of odours while inhabiting rivers and during its smolt run. It presumably reverses this sequence to return to its natal site (Ref. 89461). Several studies have shown that smolt runs are strongly correlated to increasing water temperature and water flow during spring (Ref. 89461).There is little evidence of natural spawning by land-locked populations of Atlantic salmon in Australia, and populations are maintained by stocking (Ref. 6390, 26519).

Anadromous. Fish that ascend rivers to spawn, as salmon and hilsa do. Sub-division of diadromous. Migrations should be cyclical and predictable and cover more than 100 km.

Dorsal spines (total): 3 - 4; Dorsal soft rays (total): 9 - 15; Anal spines: 3 - 4; Analsoft rays: 7 - 11; Vertebrae: 58 - 61

Juveniles feed mainly on aquatic insects and crustaceans. At sea the Atlantic salmon is pelagic, usually found feeding near the surface (Ref. 59043) preying on fish and crustaceans (Ref. 35387). May make long distance feeding migrations while at sea (e.g. individuals from European rivers may migrate to rich feeding grounds around the Faeroes Islands and in western Greenland (Ref. 58137)). Adults do not feed in freshwater during the spawning and post-spawning migrations (Refs. 30578, 51442, 59043). Preyed upon by American mergansers, kingfishers, harbor seals, grey seals, sharks, pollock and tuna.

Amphihaline species, spending most of its life in freshwater (Ref. 51442). Occurs in lakes and rocky runs and pools of small to large rivers (Ref. 86798). Some landlocked populations exist. Found in all rivers where temperature rises above 10° C for about 3 months per year and does not exceed 20° C for more than a few weeks in summer (Ref. 59043) (preferred temperatures 4-12°C). Juveniles may live in cold lakes in northern Europe (Ref. 59043). Parr (i.e. juveniles) are territorial and are found in the upper reaches of rivers and streams, in riffle areas with strong current and rough gravel bottoms (Ref. 7471). During winter, parr seek refuge in small spaces or under stones during the day (Refs. 59043, 89461). Young remain in freshwater for 1 to 6 years, then migrate to coastal marine waters or even to open oceans where they remain for 1 to 4 years before returning to freshwater for spawning (Ref. 51442). Adults inhabit cooler waters with strong to moderate flow (Ref. 44894). The Atlantic salmon is reported to live up to 10 years, but most individuals only reach 4-6 years (Ref. 88187). Juveniles feed mainly on aquatic insects, mollusks, crustaceans and fish; adults at sea feed on squids, shrimps, and fish (Ref. 51442). Most populations depend mostly or exclusively on stocking due to degradations of environmental conditions. Fishing pressure on wild stocks has decreased due to intensive farming but other problems have increased. Farmed salmons escape in large numbers and move to any river and hybridize with wild stocks (Ref. 59043). This species may hybridize with trout (Salmo trutta) (Ref. 59043). Diseases of the species include furunculosis (Aeromonas salmonicida), corynebacterial kidney disease (Renibacterium salmoninarum), enteric red mouth disease (Yersinia ruckeri), infectious pancreatic necrosis virus, bacterial kidney disease, fin rot and fungus infections (Ref. 5951). Marketed fresh, dried or salted, smoked, and frozen; eaten steamed, fried, broiled, cooked in microwave, and baked (Ref. 9988).

fisheries: highly commercial; aquaculture: commercial; gamefish: yes; price category: very high; price reliability: reliable: based on ex-vessel price for this species