The crowding and handling stress that farmed salmon experience before slaughter is a significant welfare concern that can be substantially reduced through improved pre-slaughter management.
Pre-slaughter salmon welfare represents a critical welfare intervention point because the stress accumulated in the final hours before death cannot be undone but can be substantially minimised through good management. Crowding stress in salmon is well-characterised: within minutes of crowding to high densities, cortisol concentrations rise sharply, behaviour becomes erratic, and physiological systems associated with acute stress are activated. Extended crowding periods, inappropriate water temperatures, and CO2 stunning - which in fish causes irritation and distress before unconsciousness - all increase the welfare burden in the pre-slaughter period. The gold standard approach of percussion stunning followed by immediate brain spiking provides rapid unconsciousness and irreversible brain destruction before the fish can recover consciousness, but requires careful calibration of percussion force and operator training to ensure reliable stunning across different fish sizes. Water-to-air exposure (removing fish from water), which is still used in some operations, causes extreme distress because fish cannot breathe and experience prolonged suffocation. Pre-slaughter welfare investment has both ethical and product quality dimensions: stressed fish produce poorer flesh quality, creating commercial incentives aligned with welfare improvement.