Abstract
This study examined the behavioral changes induced by butachlor to the juveniles of Clarias gariepinus. The experiment consists of five treatments (0.6, 0.7, 0.8, 0.9 and 1.0 mg/l) and a control. Ten fishes were allotted in each test tank in duplicates. Observations on behavioral responses were made at 0, 12, 24, 48, 72 and 96 hours post-exposure. The opercular movement and tail fin beat rates were observed as counts per minute using a stopwatch. The behavioral patterns of the fish in the control group were normal, whereas in the exposed groups the fish tend to lose equilibrium and swim erratically with vigorous jerky movements. At the 12th and 24th hours the fish in the exposed groups showed hyper-active movement, but became hypoactive at the 48th hour. The mean values of the tail fin beat of the exposed groups were significantly higher (p<0.05) than that of the control at the 12th hour. At the 24th and 48th hour post-exposure the exposed groups showed significant (p<0.05) time-dependent decrease compared to the control. The tail fin beat became significantly higher (P<0.05) in the control group from 72nd hours onward. The decrease of tail fin beats at the 72nd and 96th hours were dose-dependent similar observations were also recorded in the opercular ventilation. At the 12th hour the opercular ventilation of the exposed fish was significantly higher (p<0.05) than the control whereas at the 24th and 48th hours, the opercular ventilation of the exposed groups showed a significant decrease (p<0.05) compared to the control.
Highlights
The use of herbicides has been recognized as part of agricultural practices throughout the world
Behavioural responses of C. gariepinus juveniles exposed to acute concentrations of butachlor
The results of tail fin beats and opercular ventilation are presented in figures 1 and 2 respectively
Summary
The use of herbicides has been recognized as part of agricultural practices throughout the world. The arbitrary use of these herbicides to enhance agricultural production and yield may have negative effects on non-target terrestrial and aquatic organisms (Nwani et al, 2010). The increasingly widespread use of herbicides in agriculture and their impact on non-target aquatic organisms require specific studies on their effects on economically significant species such as the African catfish (Clarias gariepinus). Fish can serve as bioindicators of environmental pollution and can be used for the assessment of the quality of the aquatic environment (Lopes et al, 2001) since they are directly exposed to chemicals resulting from agricultural production via surface runoff of water or indirectly through the food chain of the ecosystem (Ateeq et al, 2002). The present study is aimed at studying the behavioural alterations caused by butachlor to juveniles of C. gariepinus
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