Effect of crude oil extracts on early stages of African catfish Heterobranchus longifilis (val.) reared under controlled condition
Eggs and larvae of Heterobranchus longifilis were exposed to extracts of different concentrations of Nigerian Bonny light crude oil and Exxon Mobil Oso off-shore condensate during a comparative toxicity experiment carried out in the Institute of Oceanography Fish Farm, University of Calabar, Nigeria. Petroleum hydrocarbon was extracted from the two oils in separate 30litre glass aquaria and the eggs and young larvae were contaminated by exposing them to three concentrations of both oils, viz: 101, 103, 102ppm for approximately 10 days. Young eggs seemed to be more sensitive from 5 to 30 hours after fertilization. Extract from 104 ppm of Bonny Light Crude and Oso condensate caused 40% and 30% mortality respectively, after 100h. Embryos contaminated with Bonny Light crude extract did not recover on transfer to clean water. Delayed development was observed in the two-highest concentrations. Heterobranchus longifilis larvae were found to have a “mean critical time” of 4.2 days in the highest concentration of Oso condensate extract when larval integument was damaged. It is concluded that Bonny light crude could be a more dangerous pollutant to juvenile fish than the Oso condensate.
KEYWORDS: Heterobranchus longifilis, crude Oil extracts, Mortality, Bonny Light Crude, Exxon Mobil