Smallholder integrated aquaculture (Fingerponds) in the wetlands of Lake Victoria, Kenya: assessing the environmental impacts with the aid of Bayesian networks

The use of wetlands to meet livelihood demands may have some effects on the ecosystem integrity. This study evaluates the use of wetlands for Fingerponds (seasonal wetland fishponds integrated with vegetable production) using experimental sites at the shores of Lake Victoria in Kenya. The major concerns such as potential eutrophication of the wetland groundwater through leaching, changes in wetland species diversity and the potential negative effects on wetland hydrology are addressed. For eutrophication, field monitoring using physical parameter and nutrient measurement (soluble reactive phosphorus, total phosphorus, ammonium nitrogen, nitrate-nitrogen, and total nitrogen) was carried out. The study revealed that there was no evidence of nutrient leaching from the ponds into the immediate wetland groundwater. There was a significant difference between the nutrient concentrations in pond water and the ground water in the immediate wetland environment. The Bayesian network approach was used to evaluate the main environmental concerns. Based on an updated Bayesian model, the overall environmental impact of Fingerponds was rated as low to moderate. This study is based on short-term monitoring of the experimental Fingerponds. There is need for continued monitoring during the implementation phase.