The effect of the water soluble fraction of Qua Iboe Light crude oil on the survival of the Juveniles of African freshwater catfish (Clarias gariepinus) was investigated under laboratory conditions for 96 hours. A total of ten (10) juveniles of C. gariepinus each were grouped into twelve (12) test aquaria and held for 24, 48, 72 and 96 hours in six (6) different concentrations of Qua Iboe Light Crude oil (0, 10, 20, 30, 40 and 50mg/l) . The experiment were conducted in two batches (A and B). No mortality was recorded in the 0-20mg/l of toxicant, 40% mortality was recorded in the 30mg/l of toxicant giving 60% survival at the end of the 96 hours of test. In the 40mg/l of toxicant 90% mortality was recorded, giving 10% of the organism surviving at the end of the 96 hours test, while in the 50mg/l of toxicant, 100% mortality was recorded leaving 0% survivor at the end of the 96 hours bioassay. The 96 hours LC50 for both batches was 30.12mg/l. Toxicant exposure induced behavioural changes such as abnormal and uncoordinated swimming movement. It was observed that mortality was concentration – dependent: the higher the concentration, the higher the mortality. There was no significant differences in mortalities between the two batches (P>0.05) leading to the conclusion that the WSF of Qua Iboe Light Crude oil in the Nigerian coastal waters may have adverse effects on aquatic fauna and flora. However, it was observed that the WSF of Qua Iboe Light Crude oil had severe impacts on the gills of the test organisms resulting in gill lamellae disintegration and erosion which may be attributed to the cause of the mortality in the test organisms
Keywords: Acute Toxicity, Clarias Gariepinus, Gills, Juveniles, Qua Iboe Light Crude Oil
