Acute Toxicity and Behavioural Responses of African Catfish,Clarias gariepinus to Amine Salt of 2,4-D

Fingerlings of African catfish,Clarias gariepinus [mean total length,(7.0±1.0) cm SD;mean weight,(3.0±0.7) g SD] were exposed to acute concentrations of amine salt of 2,4-D(0,50,200,250,350,and 400 mg/L) to determine the behavioural responses and mortality.When raised in aquaria the fish became hyperactive.The beat frequencies(opercular and tail beat frequency per minute,OBF and TBF) of the exposed fish declined with increase in the exposure duration and concentration,but the reverse was the case with percent mortality.These variables signifi cantly differed at both the exposure duration and concentration of the toxicant(P<0.05).Anova of the linear regression between variables-OBF,TBF and mortality on exposure duration indicated a strong positive relationship(P<0.001) with the entire variables except mortality and exposure duration.OBF and TBF were inversely correlated with exposure duration(r=-0.99;P<0.05).The 96 h lethal concentration was 165.36(133.29～190.51,C.L.) mg/L and the median lethal time at the highest concentration was 20.41(11.87～27.46) h.The results from this study revealed that 2,4-D was very toxic to C.gariepinus under laboratory conditions and its application should therefore,be restricted in the field.