Atlantic salmon in commercial aquaculture are typically reared at high densities that contribute to stress, disease, aggression, and physical injury - making crowding one of aquaculture's central welfare challenges.
Salmon are sentient fish with complex behavioral needs including the ability to swim freely, avoid dominant conspecifics, and express natural social hierarchies. At commercial densities, these needs are systematically thwarted. Crowded salmon show elevated cortisol levels, reduced growth efficiency, increased aggression, and compromised immune function. The resulting disease pressure requires extensive antibiotic and sea lice treatment use, creating further welfare and environmental issues. Lower-density rearing demonstrably improves welfare outcomes but requires larger facilities and higher costs - economic pressures that the industry has been slow to internalize.