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International Journal of Research and Scientific Innovation (IJRSI) |Volume IX, Issue X, October 2022|ISSN 2321-2705

Lethal Effects Of Aqueous Methanol On Juvenile Tropical Freshwater Fish (Oreochromis niloticus)

Ngoka Chizoma Adaku1*, Leo C. Osuji2, and Aduabobo. I. Hart3
1Institute of Natural Resources, Environment and Sustainable Development (INRES), University of Port Harcourt, PMB 5323 East-West Road, Choba, Rivers State, Nigeria.
2Department of Pure and Industrial Chemistry, University of Port Harcourt, PMB 5323 East-West Road, Choba, Rivers State, Nigeria.
3Department of Animal & Environmental Biology, University of Port Harcourt, PMB 5323 East-West Road, Choba, Rivers State, Nigeria.
*Corresponding author

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Abstract: In this study, juvenile tropical freshwater fish (Oreochromis niloticus) were exposed to different lethal concentrations (2.5 ml/L, 5.0ml/L, 10.0ml/L, 15.0ml/L, 20.0ml/L and 25.0ml/L respectively) of aqueous methanol and (0ml/L) which is a tank without the toxicant to serve as the control. The experiment was conducted using a static nonrenewable bioassay method. The fish were obtained from the African Regional Aquaculture Centre (ARAC), Aluu, Rivers State, Nigeria. The fishes were acclimated to an aquarium for 14 days. In order to determine the definitive test concentration, a range-finding test was conducted. The mortality, LC50s value, and the 95 per cent confidence intervals for test organisms were derived using standard procedures at 24hr, 48hr, 72hr, and 96hr respectively. There was a statistically (P<0.05) increase in the mortality rates as the concentration of the test chemical increased. The LC50 values at 24, 48, 72 and 96 hours recorded were 30.064ml/L, 26.562ml/L, 11.534ml/L, and 6.347ml/L respectively for the Chemical. The LC50 values showed that the chemical is toxic to this tropical freshwater fish. Hence, it is recommended that there should be a regulatory measure in the discharge of this chemical into the aquatic environment, to avert potential toxic effects that may result in the death of non-targeted aquatic organisms which is an edible meal for humans which in turn may affect human health.

Keywords: Lethal Toxicity, Oreochromis niloticus, Methanol, Water quality


The aquatic body is the utmost recipient of many anthropogenic and natural inputs of contaminants and toxic substances which are the main causes of the decrease in the population of aquatic biota all over the world (Idowu et al., 2020). However, sub-lethal levels of most toxic substances have proven to be devastating to fish population, composition, and density (Adedeji et al., 2009). There is great worldwide concern about the effect of human activities on the aquatic environment which is an essential component of human life and existence (Lee et al., 2011).
Toxic pollutants and contaminants generated from waste products in most industries are distinctive events in the Niger Delta whose economic activities generate such wastes from oil refining and production business. This is the condition