Assessment and Prioritization of Potential Lakes and Rivers for Fish Production and Harvesting Across the Rift Valley of Oromia National Regional State, Ethiopia

Ethiopia hosts a rich aquatic biodiversity, with over 200 freshwater fish species belonging to 75 genera, 31 families and 12 orders. The objectives of the current study were to identify potential lakes and fish species, assess their production trends, identify challenges in the fish production value chain, and indicate possible intervention mechanisms. Data were collected using tools including key informant interviews, focus group discussions, field observations, in-situ measurements, and lab analysis of water samples. Physicochemical and nutrient analyses were conducted for Lakes Beseka, Dembel, Langano, Abijata, and Hara Habas, as well as for the Koka and Gidabo reservoirs. Fish post-harvest loss assessment was carried out by adopting the Informal Fish Loss Assessment Method (IFLAM) to quickly generate fish post-harvest losses. A total of nine fish species from the eight water bodies were identified as commercially important. During the study time, the actual fish production in tons was 720, 363.8, 214.3, 88.2, 41.06, and 9.54, respectively, from Abijata, Dembel, Koka, Langano, Hawassa, and Beseka. Nile tilapia fish in lakes Dambal, Habas, Langano and Koka are highly decreasing in catch and size in the surveyed lakes during the last two decades due to high fishing pressure and use of non-standard fishing gears. The production of Nile tilapia has been exceptionally increasing in Lake Abijata since 2020, when it reappeared in the lake after two decades, because of the increase in lake volume and relative dilution of the concentration of carbonate salt in the lake. The major challenges in the fishery are the lack of fisheries management practices, the involvement of non-registered fishermen and fish traders in the fishing activity, and the use of illegal and non-standard fishing gear. Concentrations of nitrate and soluble reactive phosphorus in the Koka reservoir, particularly at the Awash River inlet, are due to surface runoff and intensive anthropogenic activities, such as the application of fertilizers, sewage, and industrial effluents from highly populated towns with poor wastewater treatment and drainage systems. DO, pH, temperature, depth, and redox potential of these water bodies were stable. The genetic loss of Nile tilapia in the major Rift Valley Lakes, such as Hara Dambal, Langano, and Hara Habas, can be restored by stocking improved strains; mass multiplication of these improved strains is needed.