The transition of Atlantic salmon from freshwater hatcheries to marine sea cages is a critical welfare period involving physiological transformation and significant handling stress.
Smolt transfer is one of the highest-risk welfare events in the Atlantic salmon production cycle. The physiological vulnerability of smolts during this transition makes optimal timing, minimal handling stress, and careful water quality management during transport essential. Welfare assessment programmes that use smolt readiness criteria - including gill ATPase activity, seawater challenge tests, and behavioural indicators - before transfer reduce the risk of welfare-compromising post-transfer mortality and disease. The interaction between smolt welfare and subsequent production performance provides a commercial incentive to improve transfer practices, making this an area where welfare and economic interests align. Continued research into optimal smolt transfer protocols and stress monitoring technology supports ongoing improvement.