The critical welfare needs of juvenile salmon during the smoltification process in aquaculture, when young fish undergo dramatic physiological changes.
Salmon smolts represent a particularly vulnerable welfare category in aquaculture. During smoltification, fish undergo profound physiological upheaval that increases their sensitivity to stressors. High stocking densities, rough handling, inadequate water quality, and premature sea transfer during this period cause measurable physiological stress and elevated mortality. The welfare consequences extend beyond the transition period, as smolts that experience significant handling stress show compromised immune function, reduced growth, and increased susceptibility to sea lice and disease after transfer. Best-practice hatcheries minimize handling during peak smoltification, maintain optimal water conditions, and use careful monitoring to time sea transfer appropriately.