ABSTRACT

This study was carried out to test the acute toxicity of refined petroleum product (petrol) .n Oreochromis ni/oticus (tilapia) fingerlings in the laboratory. The research was carried .~ut using five (5) different concentrations of petrol 1.0ml, 2.5ml, 5.0ml, 7.5ml and 10.0ml/l ! jn water, using six (6) plastic baths each of twenty (20) liters capacity but filled with only ·\ ten (10) liters of water. Petrol was introduced into the water for five (5) of the baths at i ipredetermined concentrations. The sixth bath was untreated and served as control. Ten 5 jringerlings of average weight of 4g ±0.4g were exposed to each concentration of petrol ·1 jand control water. The study lasted for four days (96hrs). Result showed that petrol was ' toxic to the test fish even at the lowest tested concentration, 100% mortality was recorded 1 ,i 1 0ml/1 concentration while 10% mortality was recorded in 1 ml/I in the test concentration ~ petrol at 96hrs exposure. The LCS0 was calculated to be 4.17ml/l using probit analysis, j while the safe concentration was calculated to be 0.417ml/l .The result also showed that J mortality of Oreochromis niloticus fingerlings exposed to petrol pollution in water e •! I increased with increase in concentration and time of exposure .The result showed that t DO and pH were significantly higher in control water than treated water at P <0.05 while ! temperature showed no significant difference between control and test samples at p >< J 1 0.05. Also reported was that variation in physicochemical parameters of water was not ) concentration dependent: Histopathological examination of the gills of test fishl showed 'I f gill elongation and lamellar hyperplasia. The fish also exhibited behavioral changes in ½ ~ forf'l'.l of aggression, rapid gulping of water and abnormal swimming movement which may ~ be due to dissolved oxygen reduction in the water but test fish were more calm at 72hrs ~ ' i ! : ! , I ! I t J ! I ! i and 96hrs which the study attributed to fish adaptation to the environment.