Effects of melatonin on oxidative stress biomarkers in juvenile catfish ( Clarias gariepinus )

Consequent upon growing concerns about the use of synthetic hormones, including melatonin, to improve fisheries and aquaculture, this study evaluated the effects of melatonin on the oxidative stress biomarkers of juvenile African catfish. One hundred and thirty-five fish were randomly assigned to groups receiving 0, 10, and 30 mg/L of melatonin in a static renewal system for 14 days, followed by seven days of melatonin withdrawal. Standard bioassays were used to quantify changes in plasma antioxidant and liver oxidative stress enzymes. The results showed significant duration- and concentration-dependent increases in plasma alanine transaminase, aspartate transaminase, and alkaline phosphatase levels compared to control groups (p ≤ 0.05). Contrarily, there were significant duration- and concentration-dependent reductions in liver superoxide dismutase and catalase, along with significant increases in malondialdehyde and glutathione activities (p ≤ 0.05). Interestingly, many of these changes persisted after melatonin was removed. These suggested that exogenous melatonin profoundly affected oxidative stress enzymes in juvenile catfish.