Farmed Salmon Welfare and Crowding During Harvest

The final stages of salmon farming including crowding during harvest represent some of the highest acute welfare risk periods for farmed fish.

Key Facts

Pre-harvest crowding concentrates salmon into small areas to facilitate pumping and transfer
Crowding causes hypoxia, physical injury from collision, and acute stress responses
Some operations use pre-slaughter crowding for 24 hours or more before actual killing
Welfare-positive harvest approaches minimize crowding duration and maintain water oxygen levels
Some operations have adopted in-pen stunning that eliminates the crowding-to-kill step

Welfare Considerations

Harvest is among the highest-risk welfare periods in salmon farming, combining the worst aspects of density stress with the novel stressors of pumping and transfer. Pre-harvest crowding creates hypoxia that causes oxygen-deprivation distress before slaughter. Physical injury from fish-on-fish contact increases as density rises. Duration of crowding is a key welfare lever — operations that minimize time from crowding onset to slaughter reduce cumulative stress. In-pen stunning systems that kill fish before crowding is complete represent the highest welfare alternative currently available.

What You Can Do

Support salmon brands with verified rapid-harvest protocols that minimize pre-slaughter crowding time
Advocate for harvest welfare to be included in aquaculture welfare certification standards
Choose salmon from operations using in-pen stunning or equivalent low-stress harvest methods
Support development and adoption of new harvest technologies that reduce pre-slaughter suffering