Atlantic salmon in net pens are stocked at densities far exceeding what behavioral research suggests they need for normal social behavior and stress-free existence.
Salmon in overcrowded net pens exist in conditions that suppress normal behavior and create chronic physiological stress. The evidence for this comes from both controlled preference studies — showing that salmon actively avoid high-density areas when choice is available — and from behavioral observation showing reduced activity, increased aggression, and abnormal swimming patterns in crowded conditions. Fin damage and scale loss are visible welfare indicators of density-related stress. Reducing stocking density is one of the most impactful welfare improvements available in salmon farming, but it directly reduces production per unit of cage volume, creating a direct economic disincentive without regulatory requirements.