The transfer of salmon smolts from freshwater hatcheries to sea cages is a high-risk welfare period involving handling stress, transport, and rapid environmental change.
Smolt transfer welfare requires timing the sea transfer precisely with smoltification status, environmental conditions, and sea water temperature. Fish transferred before complete smoltification cannot osmoregulate in sea water and experience severe physiological stress and high mortality. Transport stress is compounded by the physiological demands of environmental change. Pre-transfer welfare assessment including smolt quality scoring, water temperature management, and minimising handling duration reduces welfare harm during this critical life stage transition.