Changes in growth and biochemical status of common carp, Cyprinus carpio L. exposed to water-born zinc toxicity for different periods

Abstract

The present study was carried out to investigate the effect of sublethal zinc (Zn) concentrations on the growth, biochemical variables, and Zn residues in common carp, <em>Cyprinus carpio</em> L.. Fish (18.1 – 19.1 g) were exposed to 0.0 (control), 5.0 and 10.0 mg Zn/L for 7, 14, 28, and 56 days. At each time interval and each treatment, fish were collected, weighed and sampled to measure the growth, biochemical variables, and Zn residues in whole-fish body. Growth performance was significantly reduced with increasing Zn concentrations. However, fish exposed to 10.0 mg Zn/L for 56 days grew lower than that of the control group. Likewise, the optimum feed intake and feed conversion ratio were obtained at control group at 56 days. Furthermore, glucose, AST, ALT, creatinine, and cortisol increased significantly with increasing Zn concentration and exposure time, with maximal values at 56 days. Meanwhile, the highest values of serum protein and lipids of were obtained in the control fish reared for 56 days, whereas the lowest values were observed in fish exposed to 10.0 mg Zn/L for 56 days. The content of whole-body moisture and total ash increased significantly, while crude protein and total lipid contents decreased significantly with increasing Zn concentrations. In addition, Zn exposure increased Zn residues in fish body; however, Zn bioaccumulation in fish body was Zn dose and time dependant. The present study revealed that the growth and health status of common carp were deteriorated by Zn toxicity.