Aquaculture

Farmed Salmon Smolt Welfare

The transition of Atlantic salmon from freshwater to seawater (smoltification) is a critical welfare period, and the conditions during this transition significantly affect survival and welfare in sea pen production.

Key Facts

Smoltification involves profound physiological changes enabling saltwater osmoregulation
Premature transfer to sea water before smoltification is complete causes osmotic stress and death
Thermal manipulation can accelerate or delay smoltification to optimise production schedules
Light manipulation in recirculation aquaculture systems (RAS) is used to control smoltification timing

Welfare Considerations

Salmon transferred to sea water before completing smoltification experience acute osmotic stress as their kidneys fail to regulate ion balance. Even correctly timed transfers cause stress through temperature change, handling and novel environment. Smolts in poor physiological condition at transfer have higher mortality in sea pens during the critical early acclimatisation period. Welfare during smoltification is a major determinant of production-phase survival.

What You Can Do

Choose salmon from producers with published smolt welfare and sea transfer survival data
Support research into RAS production systems that maintain fish welfare through smoltification
Advocate for smolt welfare standards in aquaculture certification schemes
Back development of non-invasive physiological assessment tools for smolt readiness evaluation