Abstract: This paper approached the feasibility of using the xanthine oxidase (XOD), superoxide dismutase (SOD) and catalase (CAT) activities and malonyldialdehyde (MDA) content in Boleophthalmus pectinirostris liver as the indicators of Cd²⁺ toxic effects on this marine fish. Three concentrations of cadmium chloride (0.05, 0.5 and 5 mg Cd²⁺·L^-1) were enacted. The results showed that in treatment 0.05 mg Cd²⁺·L^-1, the XOD and SOD activities in B. pectinirostris liver increased with time and reached the maximum on the 10th day, while in treatments 0.5 and 5 mg Cd²⁺·L^-1, they increased significantly or extremely significantly, compared with the control. The CAT activity in treatments 0.05 and 5 mg Cd²⁺·L^-1 decreased significantly within 12 hours, but recovered then in treatment 005 mg Cd²⁺·L^-1. After moved into clean seawater for 5 days, the CAT activity increased extremely significantly in treatments 0.5 and 5 mg Cd²⁺·L^-1, but reversed in treatment 0.05 mg Cd²⁺·L^-1. As a product of antioxidation and oxidation, the content of MDA in treatments 0.5 and 5 mg Cd²⁺·L^-1 decreased extremely significantly after recovered for 5 days. It was suggested that the XOD and SOD activities in B. pectinirostris liver could be used as a biomarker of Cd²⁺ pollution, while the CAT activity and MDA content in this marine fish liver were not sensitive to Cd²⁺ stress.

Key words: Nitrogen, Calcium, Polyphenol oxidase, Peroxidase, Carnation, Leaf spot