The welfare challenges facing Atlantic salmon during the smoltification transition from freshwater to marine aquaculture.
The smolt transfer stage is one of the highest-risk welfare periods in Atlantic salmon aquaculture. Physiological stress from the freshwater-to-saltwater transition, compounded by handling and transport, creates vulnerability to disease and mortality. Welfare-focused smolt management uses validated readiness indicators rather than calendar dates to time transfer, reducing physiological failure rates. Crowding during handling and transport causes oxygen depletion and mechanical injury that are preventable through careful operational management. Sea lice treatment immediately post-transfer, when fish are already physiologically stressed, creates additional welfare burdens. Integrated welfare management approaches that minimize cumulative stress across the transfer period achieve better welfare and production outcomes.