Aquaculture

Salmon Crowding Pre-Harvest Welfare Assessment

Pre-harvest crowding of salmon for vaccination, grading and slaughter is a peak welfare risk requiring specific management.

Key Facts

Pre-harvest crowding concentrates salmon to high densities causing hypoxia and severe crowding stress
Crowding for vaccination is required at smolt stage and periodically during the production cycle
Cortisol levels rise sharply within minutes of crowding and remain elevated for hours after
Well-boat oxygen supplementation maintains oxygen saturation during crowding and transport
Crowding duration should be minimised and welfare assessment conducted before and after procedures

Welfare Considerations

Crowding stress is one of the most acute welfare challenges in salmon aquaculture. The combination of hypoxia, physical compression, social disruption and handling causes severe physiological and likely subjective distress. Managing crowding welfare requires oxygen monitoring, minimising duration and avoiding crowding of fish that are already compromised by disease or injury.

What You Can Do

Support salmon certification requiring welfare monitoring during crowding operations
Choose certified salmon from farms documenting crowding frequency and duration
Advocate for regulatory requirements for oxygen monitoring during salmon crowding procedures
Follow Humane Slaughter Association guidance on pre-slaughter salmon welfare best practice