Comparison of the effects of crude and spent oils on Tilapia (<i>Oreochromis niloticus</i>) fingerlings

Abstract

Toxic effects of bonnylight crude and spent oils on Oreochromis niloticus fingerlings were conducted under laboratory conditions at the University of Port Harcourt, Nigeria for two months. Five concentrations (5 ml/L, 10 ml/L, 20 m1/L, 50 m1/L and l00 ml/L) of water soluble fraction (WSF) of crude and spent oils were prepared. To each of the concentrations of the WSF, ten fingerlings of O. niloticus were exposed for 96 hours for both crude and spent oil groups. The 96 hour LC₅₀ was determined being 66 ml and 38.5 m1 for crude and spent oils respectively. There was no significant difference in rate of mortality between crude and spent oil groups at 24 and 96 hours respectively (p>0.05). The difference in mortality between crude and spent oil groups at 48 and 7 hours was significant (p<0.05). Reduction in dissolved oxygen from 7.2 to 3.8 mg/L and 6.4 to 3.9 mg/L for crude and spent oil groups was significant (p>0.05). The death of fingerlings might be related to the decreased dissolved oxygen of the water due to the presence of crude oil or spent oil. Proper positioning of mechanic workshops and effective monitoring of water bodies are suggested measures to curb this menace.

Key Words: Oreochromis niloticus, crude oil, spent oil, dissolved oxygen and WSF