Aquaculture

Farmed Salmon Crowding Stress: Physiology and Welfare

High stocking densities in salmon aquaculture trigger physiological stress responses that impair immunity, growth, and welfare over sustained periods.

Key Facts

Cortisol rises rapidly in salmon exposed to crowding
Immune function is suppressed at high densities, increasing disease risk
Crowding triggers aggression, fin damage, and subordination stress
Norwegian regulations set maximum densities but enforcement varies
Welfare indicators like eye haemorrhage correlate with crowding stress
Harvest crowding causes acute welfare crises as fish are compressed into pump crowders

Welfare Considerations

Salmon experience fear, pain, and physiological distress during crowding. Elevated cortisol impairs osmoregulation and immune defence, compounding welfare problems. Pre-slaughter crowding may cause the most intense acute suffering in the production cycle, making humane harvest protocols critical.

What You Can Do

Support aquaculture certified to higher stocking density standards
Choose salmon with Best Aquaculture Practices or similar certification
Advocate for pre-harvest welfare protocols in seafood sustainability standards