Toxicity, Growth And Survival Of Clarias Gariepinus Juveniles Exposed To Different Concentrations Of Crude Oil Fractions-Polluted Water

Abstract

Studies were carried out on the toxicity, growth and survival of Clarias gariepinus juveniles exposed to different concentrations of oil-polluted water. Thirty-nine aerated aquaria (60 × 30 × 30 cm 3 ), arranged in a 4 × 3 Complete Randomized Block Design were used for the study. Three oil types: the Bonny light crude oil (BLCO), the premium motor spirit (PMS) and kerosene (DPK) at oil concentrations of 1.00, 1.50, 2.00 and 2.50 ml L f l t t , l f i f i f l -1 were used in triplicates of 5 ml to contaminate 15 L of dechlorinated tap water and 20 fingerlings o Clarias gariepinus (22 ± 0.24 g) exposed to it. A control treatment (0.00 ml L -1 ) of non-oil contamination was a so used in riplicates. A 96-hour toxicity phase in the oil-polluted water preceded a 42 days recovery phase. 38% crude pro ein diet was fed to fish during exposure and recovery phases at 3% and 5% body weight per day respectively. Water temperature, pH, fish mortality and normalized biomass index (NBI) of each aquarium were monitored. The total organic nitrogen, soluble organic nitrogen and colloidal organic nitrogen in addition to soluble and adsorbed ammonia in the aquaria water and sediments were analyzed using standard methods. Results showed that the water temperature was 26 ± 2.04 ° C, pH was 6.50 ± 0.30 and fortnight y eed intake of fish increased between days 14 and 42. This increase, which corresponded w th the increase in the fortnightly weight gain, could be attributed to the reduction of stress caused during the 96-h toxicity phase. The increase in the soluble ammonium and the exchangeable ammonium concentrations o water correlated with the increase in the concentrations (1.50 -2.50 ml L -1 ) of BLCO, PMS and DPK. Percent mortality of f sh reduced between days 14 and 42 irrespective o oil treatment while fish exposed to the control treatment had lower percent mortality than those exposed to the oil treatments. This trend was corroborated by the relatively higher NBI for the control during the exposure (-0.02) and recovery {0.08 (14 days), 0.08 (38 days) and 0.21 (42 days)} periods than those of oi treatments (-49.64 to -0.10).