Farmed Atlantic salmon spend the majority of their lives in open sea net cages. Welfare challenges in sea cages include sea lice, disease, crowding, and slaughter methods.
Sea cage salmon welfare involves multiple compounding challenges. Sea lice infestations cause skin lesions, secondary infections, and osmoregulation failure. Crowding at commercial densities causes fin damage and social conflict. Treatment for sea lice - including warm-water thermolicer treatment and chemical baths - causes acute stress and sometimes mortality. Storm damage to cages can cause mass mortality events. Salmon in sea cages experience the environmental drive to migrate without the ability to do so - whether this causes suffering is uncertain but represents a significant departure from natural behaviour.