Atlantic salmon Salmo salar

Atlantic salmon is an anadromous salmonid of the temperate and arctic North Atlantic, ranging from northern Quebec to Connecticut in the west and from the White and Barents seas through north-eastern Europe to the Baltic and North Sea, and now farmed far outside that range in Chile, Australia and New Zealand. FAO FishStat records 2,704,464 tonnes of farmed production in 2024. Published maxima and ordinary adults differ sharply: FishBase gives 150 cm and 46.8 kg with a maximum reported age of 13 years, while NOAA Fisheries puts returning United States adults at 28 to 30 inches and 8 to 12 pounds after two winters at sea, and their lifespan at four to six years. Culture follows the wild life history. Fish are hatched and reared in fresh water, spend two to three years as parr, then undergo smoltification, in which the gill is remodelled for seawater osmoregulation, before transfer to sea cages. Two problems define the marine phase. Salmon lice feed on the blood, tissue and mucus of the host, causing skin damage and opening the way to secondary infection; Ireland triggers treatment at 0.5 ovigerous females per fish in spring. Infectious salmon anaemia, an orthomyxovirus whose HPR-deleted variant is the virulent one, is answered with biosecurity, stocking and density control rather than treatment.