The transfer of Atlantic salmon smolts from freshwater hatcheries to marine sea cages is a critical welfare risk period involving significant physiological and environmental change.
Smolt welfare at sea transfer is determined by smoltification readiness, transport quality and sea cage reception. Transferring smolts before physiological readiness is complete causes osmoregulatory failure and welfare harm. Careful timing based on physiological assessment rather than purely calendar-based transfer optimises welfare. Reception conditions including lice challenge management and water quality affect post-transfer welfare.