In this aspect, the results of this study, in terms of gene expression of the mitochondrial β-oxidation markers (cpt1a and hadh), did not reveal a parallel increase with that of acox1 in the muscle of HF+HT_ST fish, suggesting incomplete oxidation of fatty acids and their subsequent accumulation, in agreement with the higher percentage of fat content obtained by the proximate analysis in that group. The gene discussed is ACOX1; the disease is hydrops fetalis.