Aquaculture Feed and Fertilizer Resources Information System

Atlantic salmon - Salmo salar

Linnaeus, 1758 [Salmonidae]

FAO official common names: Fr - Saumon de l'Atlantique; Es - Salmón del Atlántico

Biological features:

Atlantic salmon (Figure 1) has an elongate body that is somewhat compressed laterally; the greatest depth is at the dorsal fin origin and it becomes deeper with age. Scales small, 114–130 in lateral line, 109–121 above lateral line and 11–15 obliquely from adipose fin to lateral line. A fleshy adipose fin on the back just in front of the tail fin. Mouth large; gill rakers may range from 15 to 20 and vertebrae from 56 to 81 (Scott and Crossman, 1973). Caudal fin is fairly deeply forked.  Small parr have 8–11 pigmented bars along each side of the body that alternate with a single row of red spots along the lateral line. These marks are lost when fish reach smolt stage and body colour becomes silvery and back shows shades of green, blue and brown. Adult body colour varies, but fish are generally silver-skinned with distinct dark blue-green, cross-like spots over the body and head, and above the lateral line. After spawning body colour of males (kelts) turns dark. The head of the male becomes elongated and grows a "kype" from the tip of the lower jaw, making males and females easily distinguished. The flesh colour of juveniles is nearly white, which changes to pink and then to deep reddish orange (Figure 2) at market size or maturity.

In the natural environment, this anadromous fish spawns in freshwater and alevins (~ 2 cm) emerge from eggs, subsisting off the attached yolk sac until reaching the fry stage when they are ready to accept exogenous food. The young remain in freshwater for 2 to 5 years depending on the water temperature and food supply. Prior to migration, smolts undergo physiological and behavioral changes, a process called smoltification that prepares them for their life at sea. After spending 1–2 years at sea, they return to their freshwater rivers to spawn. At sea, the Atlantic salmon prefers temperatures from 4 to 12 ˚C but can withstand short periods of time at lower or upper lethal temperatures of -0.7 and 27.8 ˚C, respectively (Bigelow, 1963). Salmon farming requires both freshwater and saltwater operations. Because of the efficiencies of farm husbandry practices, the farming process accelerates the life cycle to 1 year or less in freshwater and from 10 to 15 months at sea.