Stocking Density and Crowding Stress in Farmed Salmon

High stocking densities in salmon farms are associated with chronic stress, increased disease susceptibility, and suppressed immune function.

Key Facts

Maximum permitted stocking density for salmon in Norway is 25 kg per cubic metre
Many farms routinely operate at maximum density, particularly as harvest approaches
Crowding causes measurable elevations in cortisol for periods of hours to days
High density is associated with increased sea lice infestation and bacterial disease
Voluntary certification schemes set lower density limits than regulatory minima

Welfare Considerations

Crowding stress in farmed salmon is well-documented and dose-dependent: the higher the density, the greater the physiological stress response. Chronic elevation of cortisol suppresses immune function, increasing vulnerability to pathogens. Behavioural indicators of crowding stress include reduced feed intake, increased fin damage from aggression, and altered swimming patterns. Welfare-conscious producers voluntarily adopt lower densities, though this reduces profitability per unit. Regulatory minimum standards have not kept pace with the science.

What You Can Do

Choose salmon carrying welfare certification that includes density limits
Ask retailers what maximum stocking density their suppliers operate at
Support regulatory reform to lower legal maximum stocking densities
Learn about the connection between crowding, disease, and antibiotic use
Advocate for consumer labelling requirements for salmon stocking density