Dissolved oxygen management is critical for Atlantic salmon welfare in sea cages, with oxygen depletion causing acute distress and chronic welfare impairment.
Salmon experiencing dissolved oxygen depletion in sea cages show surface crowding, reduced feeding, and increased ventilation effort indicating welfare impairment. Chronic mild hypoxia below 7 mg/L causes suppressed immune function, reduced growth, and impaired welfare even without acute mortality. Summer oxygen depletion events are increasingly frequent with warming seas. Emergency oxygen supplementation through compressed gas systems provides welfare protection during high-risk periods. Welfare-focused oxygen management maintains levels above welfare thresholds at all depths where salmon are present, not just at surface measurement points.