The period immediately before slaughter is a high-welfare-risk phase for farmed Atlantic salmon, with crowding, handling, and transport causing significant stress.
Salmon in harvest crowding operations experience hypoxia, physical injury from crowding nets, and extreme social stress from very high densities. Transport in live hauler trucks involves continued crowding with water quality challenges. Carbon dioxide narcosis before slaughter causes hyperventilation and distress before loss of consciousness. Percussion stunners that miss their target leave fish conscious during neck-cutting. Electrical stunning when properly calibrated causes immediate insensibility without prior aversive experience. The welfare quality of slaughter has major implications for millions of individual fish.