This study will assess on both fish ecology and fisheries. The main aime are to explore the potential to either reduce densities of "Garra" in the reservoirs so as to improve water quality, or to partially replace them by fish taht can be consumed. This will require studies on the ecology of resident fish (densities, feeding ecology, ...), experimental stocking of fish (Oreochromis) in selected reservoris and monitoring of their effect on "Garra" and water qualtiy, and exploring possibilities for removing "Garra" keeping them at low densities. This research will result in a better understanding of the impact of fish on reservoir ecology and will provide insight into options for management of the reservoirs in terms of water quality and the culture of fish.