IMPACT OF WATER SOLUBLE FRACTIONS OF CRUDE OIL ON GROWTH PERFORMANCE OF THE CATFISH

An investigation on the impact of sub-lethal concentrations (0-control, 12.5, 25, 50 and 100%) of water-soluble fractions (WSFs) of crude oil on the performance of the catfish Heterobranchus bidorsalis fingerlings was carried out in 2005 under laboratory conditions in Asaba, Delta State, Nigeria, during a 10-week period of exposure in a renewal static bioassay system. Growth of H. bidorsalis was observed to reduce significantly (P>0.05) with increasing time of exposure and concentrations of WSFs of crude oil when compared with control fish. Fish weight was observed to significantly (P>0.05) reduce with increasing concentrations of WSF. A slight increase in length of fish with increasing period of exposure was observed in all the groups. The condition factor (k) of H. bidorsalis after 10 weeks exposure to 12.5 and 25% concentrations of WSF also showed significant (P>0.05) reduction only in the exposed groups. Mortality was recorded in the 50 and 100 % WSFs. Although, no mortality occurred in the control and other exposed groups, fish in the 12.5 and 25% WSFs were less active in swimming and feeding when compared with the control fish. The dissolved oxygen of the medium was significantly reduced (P>0.05) while the biological oxygen demand was significantly (P≤0.05) increased with increasing level of the WSFs. This study has demonstrated that the water-soluble fractions of crude oil have a highly significant effect of reducing the growth performance of H. bidorsalis. The study has also showed that H. bidorsalis ca