Investigation in some serum values and food qualities of freshwater fish (Orechromis niloticus) exposed to chromium, mercury, nickel and zinc in differing calcium concentrations

Freshwater fish Oreochromis niloticus were exposed to chromium (Cr+6), nickel (Ni+2), zinc (Zn+2) and mercury (Hg+2) in waters with different calcium (Ca+2) concentrations (30, 60 and 120 mg Ca+2/L in acute (3 days) and chronic (30 days) durations. In acute experiments, 30 µM concentration of Cr+6, Ni+2 and Zn+2, and 0.3 µM concentration of Hg+2 were used, but metal concentration was 0.03 µM for Hg+2 while it was 10 µM for Cr+6, Ni+2 and Zn+2 in chronic experiments. After experimental durations, 11 biochemical parameters in the serum and food qualities in the muscle of O. niloticus were investigated. In acute and chronic experiments, no fish mortality was observed in all metal and hardness levels. Data showed that there were significant alterations in in the levels of glucose cholesterol, triglyceride, blood urea nitrogen, protein, ALT, AST, Na+, K+, Ca+2 ve Cl- in the serum. However, these alterations occurred much more in chronic durations comparing to the acute ones. Data also showed that there were significant variations in food quality of muscle tissue in both duration, as total protein, lipid and raw ash levels changed significantly. However, there was no significant alteration in water content of muscle tissue. Most of alterations were observed in lipid and raw ash levels of muscle tissue