**5. Conclusions**

In the last years, several efforts have been made in the Aquaculture industry to improve fish welfare. Changes in environmental conditions and diets can alter the redox balance, thus affecting the welfare state. Most redox studies in fish focuses on classical markers such enzymatic and non-enzymatic antioxidants, and lipoperoxidation products as oxidative damage markers. In this paper we present evidence that the study should be extended to the associated pathways of redox balance including: markers of protein oxidation levels, metabolic enzymes related to glutathione synthesis, repair/refolding of oxidized proteins or main protein degradation processes.
