Effects of water pollutants on wetlands and fishery resources: case study Kirinya and Wanyange wetlands of lake Victoria

Abstract

Pollution is the biggest killer in developing countries with contaminated air, water, and soil claiming millions of lives every year. However, its impact on fish and fisheries resources in Uganda has not been ascertained. The main objective of this study was to assess the effect of pollutants on the fisheries resources at Kirinya and Wanyange wetlands specifically through; a) determining the specific physico-chemical parameters; b) ascertain fish species composition and diversity; c) determining the heavy metal pollutants with in-situ water quality; and d) evaluating heavy metal pollutants in fish. Field visits for field tests were done for sample collection and by acid digestion and spectra photo metric analysis results were obtained. High significant differences (P>0.001) were observed in the total depth, Secchi depth, dissolved oxygen, across sections of the wetlands (inshore, midshore, and offshore), whereas high significant differences (P>0.01) were observed in the temperature, electrical conductivity. There were very high significant differences (P>0.001) in species composition across the wetlands, with Kirinya having the highest number of species of 195 with a percentage composition of 42% of Oreochromis spp. Cichlidae was the most abundant Family composed of 57.1 % of the species and these were predetermined by Shannon index and Margalef index. Heavy metals such as Pb, Zn, and Mn had concentration levels that exceeded the limits of WHO and UNBS standards in both first and second sampling. Heavy metal (Pb, Cu and Mn) concentrations were detected in fish with high significant differences (P>0.001) among the fish species (L.n, O.n and C.g) and also in organs i.e. Muscle, Liver and Gills. Conclusively, the study found that Kirinya was more polluted than Wanyange with limits above the WHO and UNBS Standard, species were more abundant at Kirinya and that Kirinya waters were shallow compared to Wanyange. Finally, the study recommends that; there should be regular monitoring for changes in physico-chemical parameters for easy identification of causes to these changes and to devise means of proper management of these resources to reduce negative impacts on the ecosystem. Management strategies for wetlands should be put in place as they act as breeding areas and refugia from predatory fish. Pollution from agricultural runoff, industrial runoff, domestic waste, municipal waste water and land use should be minimized and monitored, waste water should be treated before disposal. Lastly, Collective multidisciplinary measures should be taken to control pollution from industrial waste as these are the major sources of heavy metals.