Aquaculture

Farmed Salmon Crowding Stress Hormones

The physiological evidence for crowding-induced stress in farmed salmon and what hormone measures tell us about welfare.

Key Facts

Plasma cortisol is the primary stress indicator measured in farmed salmon welfare research
Crowding causes cortisol to rise within minutes to levels associated with severe stress
Chronic elevation of cortisol suppresses immune function and reduces disease resistance
Cortisol response magnitude varies with individual, life stage, and prior experience
Behavioral indicators of crowding stress include surface avoidance and reduced feeding

Welfare Considerations

Cortisol data provides objective evidence that crowding causes substantial physiological stress in salmon. The welfare significance of this stress response is comparable to that in mammals. Reducing crowding events and durations directly reduces measurable suffering.

What You Can Do

Support aquaculture welfare standards with crowding duration and density limits
Advocate for regular cortisol monitoring as a welfare assessment tool in salmon farming
Choose salmon from certified farms with documented crowding reduction protocols