ABSTRACT

This study was conducted to investigate the effect of atrazine on mortality, behaviour and development of some organs in Clarias gariepinus fry. One (1) week old C. gariepinus fry was purchased live from the Fisheries and Aquaculture department of the faculty of agriculture, University of Benin. The experimental fishes were exposed for 72 hours to 0.03µg/l, 0.3µg/l, 3µg/l and 30µg/l atrazine and followed by a recovery period of (25) days. Mortality and behavioural responses were recorded throughout the experiment. Physico-chemical parameters of test water were also monitored throughout the experiment. At the end of the recovery period, fry samples were prepared for histopathology using standard methods of histology. Results showed that the physico-chemical parameters of test water were within range for survival of fishes in the tropics. Mortality rates increased with increasing concentration and duration of exposure. Treatment with the highest concentration of atrazine (30µg/l) witnessed one hundred percent mortality after 48 hours. Behavioural responses such as erratic swimming, lethargy, loss of balance and discolouration were observed in treatments in a dose-dependent trend. Histological assessment revealed disintegration of the nervous tissues, vacuolization of epithelium of the anterior intestine, loss of gill cytoarchitecture and distortions of the intestine in treatment groups. Findings from this study therefore reveals that atrazine exposure to Clarias gariepinus even at the early fry developmental stage could lead to increased mortality rates, abnormal behaviour and histopathological alterations in vital organs which will pose a serious threat to the population of fish in the wild if unsafe application of atrazine is left unchecked.