Aquaculture

Salmon Smolt Welfare at Sea Cage Transfer

The transfer of salmon smolts from freshwater hatcheries to sea cages is a high-stress event that significantly affects subsequent welfare and health.

Key Facts

Smoltification is a critical physiological transition allowing salmon to tolerate saltwater
Transfer before smoltification is complete causes osmoregulatory stress and mortality
Boat transfer causes crowding stress that can be measured by cortisol elevation
Well-boat oxygen management during transfer is critical for smolt survival
Post-transfer mortality spikes indicate transfer-related welfare failure

Welfare Considerations

Smolt transfer mortality is both a welfare and economic problem, creating aligned incentives for improvement. Timing transfer to coincide with optimal smoltification, minimising crowding duration, and monitoring oxygen and temperature during transport are evidence-based welfare improvements that also improve production outcomes.

What You Can Do

Support aquaculture standards requiring smolt welfare monitoring at transfer
Choose certified salmon from farms with documented transfer protocols
Advocate for smolt welfare standards in sea farm licensing requirements