Effects of Crude Oil and Spent Oil on <i>Clarias garipinus</i>: A Typical Marine Fish

<b>Problem statement:</b> Petroleum hydrocarbon and petroleum residue (i.e., spent oil) remains the foremost pollutants to the fish communities in various aquatic media-ponds, streams, rivers, creeks, coastal and marine environments through indiscriminate disposal of oil contaminated drilling muds, cutting and oil spillages. <b>Approach:</b> Also, the spent oil enters into aquatic media through run-off following unguided disposal. Both the petroleum hydrocarbon and spent oil, on getting to the water bodies spread fast and produce lethal, sub-lethal and even acute effect of petroleum hydrocarbon and spent oil on the fingerlings and other juvenile fishes. <b>Results:</b> Since this group of fish constitutes about 60% of the fish population in any aquatic medium, a green house study was carried out to assess the effects of crude oil and spent oil on fingerlings of <i>Clarias garipinus</i>-a typical marine fish. In this study, fingerlings of <i>Clarias garipinus</i> were exposed to 2-10% concentration of crude oil and spent oil for 96 h period. Readings were taken every 24 h. From concentration of 4-10%, high mortality rate averaging 10 out of 10 fingerlings were recorded. <b>Conclusion/Recommendations:</b> The deaths were attributed to reduced dissolved oxygen and blockage of the water surface by the oils. Concentrations of 2% showed a reduced level of mortality, which even lapsed over the 96 h period. The mortalities were owed to impairment in neurologically dysfunction. Changes in physiological character such as changes in skin color and reduced locomotive actions were also observed.