Changes in behavior and hematological parameters of freshwater African catfish Clarias gariepinus (Burchell 1822) following sublethal exposure to chloramphenicol.

The present study was aimed at evaluating the effects of different concentrations of the most commonly used fish antimicrobial drug, chloramphenicol (CAP), on the behavior and hematological parameters of Clarias gariepinus. Fish specimens were exposed to three (2.5, 5.0 and 10.0 mg L(-1)) sublethal concentrations of CAP and a control. Abnormal behavioral changes were observed in fish exposed to higher concentration of CAP. Blood erythrocytes were sampled on days 1, 5, 10 and 15 postexposure to evaluate hematological parameters. Results showed concentration- and time-dependent significant increase in packed cell volume after day 5 of exposure (p < 0.05). Hemoglobin values also significantly decreased from day 5, whereas values of mean cellular volume significantly decreased throughout the experimental period (p < 0.05). A mixed trend was observed in the mean values of red blood cells, white blood cells, mean cellular hemoglobin and mean cellular hemoglobin concentration as well as neutrophils. Activities of lymphocytes were significantly increased in all CAP-treated fish during the exposure period, whereas no significant differences were observed in values of monocytes, eosinophils and basophils among the treatment groups and control. Consequently, precautions must be taken, especially when high concentrations of CAP are used in long-term treatments of C. gariepinus in aquaculture.