Atlantic salmon are one of the most studied farmed fish species. Despite this, welfare challenges including sea lice, crowding, and inhumane slaughter remain widespread. This comprehensive guide covers the evidence.
Sea lice infestation is the most significant welfare challenge in Atlantic salmon farming globally. Adult female lice attach to salmon skin, feeding on mucus, skin, and blood. Tissue damage creates open lesions that affect osmoregulation, cause chronic pain, and increase susceptibility to secondary infections. Heavy infestations can kill fish. The welfare impact of sea lice is severe and persistent.
Treatment options each carry their own welfare costs: chemical treatments stress fish physiologically; mechanical delousing procedures (hydrolicer, thermolicer) cause physical injury and handling stress; freshwater bathing stresses osmoregulatory systems. Integrated pest management approaches that reduce lice burden while minimizing treatment welfare harm are the welfare-optimal strategy, though no current commercial approach fully resolves the problem.
Crowding during harvest causes extreme welfare harm. Density increases cause fin damage, scale loss, oxygen depletion, and behavioral panic responses including leaping and rapid avoidance swimming. Pre-slaughter crowding stress is incompatible with salmon welfare. Electrical stunning (AQUI-S, electronarcotics) or percussive stunning before crowding and slaughter provides welfare protection and should be standard practice globally.