The smolt stage is one of the most welfare-critical periods in Atlantic salmon farming. Understanding smoltification physiology helps farmers minimise welfare costs during this vulnerable transition.
Smolt welfare represents a systemic challenge for Atlantic salmon farming that sits upstream of the sea cage welfare issues that receive more attention. A poorly timed smolt transfer creates chronic physiological stress that persists throughout the sea cage production phase, compromising welfare, growth, and immunity. The welfare investment in getting smoltification right — managing photoperiod programmes carefully, conducting physiological readiness assessments, and transferring only fully prepared smolts — pays dividends throughout the subsequent production cycle. As salmon farming intensifies and production accelerates, pressure to transfer smolts before they are physiologically ready creates welfare risks that are difficult to detect externally but are measurable through cortisol and gill enzyme assessment. Welfare-positive salmon farming requires smolt readiness assessment as a standard management tool.