Growth performance and condition factor of <i>Oreochromis niloticus</i> (Linneaus, 1758) after exposure to chemically dispersed Bonny Light crude oil

Abstract

Dispersants are employed in oil spill situations to emulsify the oil into the water column thereby, facilitating weathering; this is without consideration for aquatic life and productivity. A renewal static bioassay was used to assess the recovery of Oreochromis niloticus after exposure to water accommodated fraction of dispersed Bonny Light crude oil (WAFDCO) and water accommodated fraction of Bonny Light crude oil (WAFCO) at sub-lethal concentrations of 0.2, 0.4, 0.8 and 1.6ml/l, based on the growth performance and condition factor after 49-days exposure and 54-days grow-out phases. The results showed that, the physicochemical parameters of the test media were affected by the concentrations of WAFDCO and WAFCO. The mean weight gain of O. niloticus increased with time in the exposure regimes/concentrations. Growth performance was concentration dependent, the highest mean weight of fish (15.67±0.78g) was from 1.6ml/l concentration of the WAFCO, which was higher than the control. The mean relative growth rate was higher (10.40±0.69%) in the fish from WAFCO while the highest mean specific growth rate (0.85±0.05%) was from WAFDCO. The highest value (3.42) of condition factor (K), was obtained in the 1.6ml/l of the WAFDCO. The K values of the fish from the WAFDCO were slightly higher than those from the WAFCO, which were lower than the control. Condition factor was greater than three which implied that, the fish were in good state, thus, their recovery was good after removal from the contaminated environment; hence, all mitigative actions should be prompt during and after oil spills.