A study suggests that the intestinal barrier function of Atlantic salmon post smolts is reduced by changing ocean conditions and can be used as an indicator of welfare. The study set out to find how changing conditions in sea caged salmon triggers stress responses.The study revealed that adverse environmental conditions that can occur in sea cages, elicits primary and secondary stress responses in Atlantic salmon post smolts. The intestinal barrier function was significantly affected by prolonged hypoxic stress even when no primary stress response was observed.