EGYPTIAN JOURNAL OF AQUATIC RESEARCH 1687-4285 VOL. 31 NO. 2, 2005: 60-71. *Corresponding author E-mail: ehamdy62@yahoo.com TOXICITY OF CADMIUM AND COPPER AND THEIR EFFECT ON SOME BIOCHEMICAL PARAMETERS OF MARINE FISH MUGIL SEHELI EMAD H. ABOU EL-NAGA*, KHALID M. EL-MOSELHY and MOHAMED A. HAMED National Institute of Oceanography and Fisheries Keywords: toxicity, cadmium, copper, aspartate and alanine transaminases, glucose, glycogen, lipid, protein, fish (Mugil seheli) ABSTRACT The present work aimed to estimate the toxicity of cadmium and copper to fingerlings of marine fish Mugil seheli, as well as the effect of different concentratios of Cd and Cu on some biochemical parameters (Aspartate and alanine transaminase enzymes, glucose, glycogen, lipid and protein) in the fish organs. 96-h LC 50s of Cd and Cu were 5.36 and 1.64 ppm, respectively. Levels of aspartate and alanine transaminase were reduced within 2 days of exposure to different concentrations of Cd (2.0 and 0.5 ppm) and Cu (0.5 and 0.2 ppm) in both plasma and muscle tissue. Glucose was increased reaching the highest values after 4 days of the treatment with Cd and Cu, while muscle glycogen was increased at first days then dropped after 14 days below control level. Generally, total lipids and proteins in plasma and muscle recorded higher values than the control one. The present study showed high toxicity of copper to fish Mugil seheli comparing to cadmium. INTRODUCTION The toxicity tests are necessary in water pollution evaluation because chemical and physical measurements alone are not sufficient to assess potential effects on aquatic biota (Tarzwell, 1971). In addition, it is an important step to detect the levels of toxicants to be used in the experimental studies of the accumulation and effect of these toxicants to the marine organisms. There are many studies concern with the toxicity of cadmium on vertebrates and invertebrates (Rasmussen and Andersen, 2000, Adami et al, 2002 and Filiovic and Raspor, 2003). Fish exposed to high concentration of cadmium quickly develop lack of calcium and low blood hemoglobin. Microorganisms may suffer growth inhibition at cadmium concentration of 0.25 mg/l (Roberts, 2003). Biochemical and physiological biomarkers are frequently used for detecting or diagnosing sublethal effects in fish exposed to different toxic substances (Theodorakis et al., 1992). Sublethal effects are biochemical in origin as the most toxicants exert their effects at basic level of the organism by reacting with enzymes or metabolites and other functional components of the cell. Such effects might lead to irreversible and detrimental disturbances of integrated functions such as behavior, growth, reproduction and survival (EIFAC, 1975 and Waldichuk, 1979). Transaminase enzymes play vital role in carbohydrate-protein metabolism in