The effects of increased freshwater salinity in the biodisponibility of metals (Cr, Pb) and effects on antioxidant systems of Oreochromis niloticus

► Salinity increase in freshwater affects antioxidant system of fish O. niloticus. ► Metal and salinity exposure of fish cause stress that can lead to alteration in antioxidant reaction. ► Profound effects were found at lower salinity. ► Salinity of freshwater should be taken into account in measuring antioxidant system of freshwater fish in the field.