Toxicological assessment of four common household surfactants on Clarias gariepinus (Burchell, 1822) and Oreochromis niloticus (Linnaeus, 1758)
The acute toxicity of four common household liquid detergents coded as (FL, ML, MF and LC) was evaluated on two fish species; African Catfish (Clarias gariepinus) and Nile Tilapia (Oreochromis niloticus) fingerlings in a static bioassay. During the exposure period (96 hours), there was a remarkable rise of alkalinity from 22.00 mgL-1 to 62.50 mgL-1 while dissolved oxygen decreased with increased concentration. Behavioral changes such as restlessness, rapid swimming, loss of balance, opercula ventilation, respiratory distress and hemorrhaging of gill filaments were observed before mortality. Based on 96 hr LC50, FL (0.009 ml/L), was the most toxic followed by ML (0.014 ml/L), MF (0.056 ml/L) and LC (0.168 ml/L) against O. niloticus whereas MF (0.021 ml/L) was the most toxic followed by ML (0.033 ml/L), FL (0.038 ml/L) and LC (0.364 ml/L) against C. gariepinus in descending order. In terms of the sensitivity, O. niloticus fingerlings were more susceptible to the detergents than C. gariepinus fingerlings. The use of detergents cannot be discontinued. However, better methods of disposing the ‘after wash' needs to be worked out. At the present rate at which they are manufactured and introduced into the aquatic environment indiscriminately, aquaculture fish species could seriously be threatened.
Keywords: Acute toxicity, detergents, Oreochromis niloticus, Clarias gariepinus, behavioral changes