High stocking densities in salmon aquaculture cause chronic stress, disease, and injury. Understanding and reducing crowding stress is central to improving farmed salmon welfare.
Stocking density is one of the most significant determinants of welfare in farmed salmon. The chronic stress associated with overcrowding triggers a cascade of physiological and behavioural consequences, including immune suppression, increased aggression, and reduced feed efficiency. Fish in high-density systems have fewer opportunities to avoid aggressive conspecifics, leading to persistent stress responses that compromise health and welfare. The welfare costs of high density are compounded by disease outbreaks that spread rapidly in crowded conditions and by the need for frequent handling and treatment. Progressive density reductions, alongside improvements in water quality monitoring and feeding management, represent achievable welfare improvements that often align with economic incentives through reduced mortality and better growth outcomes.