Low dissolved oxygen levels in aquaculture net pens cause significant fish welfare harm through chronic stress, impaired immune function, and in severe cases mass mortality events.
Oxygen depletion in aquaculture is a welfare emergency that can affect hundreds of thousands of fish simultaneously. Hypoxic fish experience genuine physiological distress as tissues become oxygen-starved, and death from suffocation in oxygen-depleted water is not rapid. Chronic low-level hypoxia, below the threshold of acute crisis, still impairs immune function, growth, and behavioral welfare. The welfare tragedy is that most oxygen events are predictable and preventable with appropriate monitoring, site selection, and emergency response equipment — yet cost pressures lead many operations to underinvest in these safeguards.