Salmon farming relies on high stocking densities that create chronic stress, increase disease risk, and cause measurable welfare harms. Understanding and reducing crowding stress is central to improving salmon welfare across the aquaculture industry.
Salmon are active, exploratory fish with strong environmental preferences and complex behavioural repertoires that crowding systematically suppresses. At high stocking densities, salmon cannot maintain their preferred spatial orientation, are subject to chronic fin nipping and competitive exclusion from feeding, and show persistent elevated cortisol consistent with chronic stress. This stress state suppresses immunity, making disease outbreaks more likely and more severe — creating a cycle in which welfare problems drive further health interventions. Reducing stocking density is one of the most direct and evidence-supported ways to improve salmon welfare, and several higher-welfare certification schemes now set density limits as a core standard.