How the smoltification process affects the welfare of farmed Atlantic salmon during one of the most physiologically demanding transitions in their lifecycle.
Smoltification represents a remarkable biological transformation but also a welfare-sensitive period in farmed salmon production. The physiological demands of the transition are enormous — essentially the entire internal chemistry of the fish is reorganised. Premature or delayed transfer to seawater adds osmoregulatory stress to an already challenged system, increasing susceptibility to disease and causing mortality. Poor handling during transfer — which typically involves crowding, pump transfer, and transport — compounds the stress burden significantly. The welfare case for investment in smolt quality assessment tools and careful transfer timing is strong: fish that transition successfully show better growth, lower disease burden, and improved welfare outcomes throughout the sea pen phase. RAS technology, which allows precise environmental control, offers significant welfare advantages for managing smoltification.