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East African lakes support the food and water security of millions of people. Yet, a lack of continuous long-term water quality data for these waterbodies impedes their sustainable management. While satellite-based water quality retrieval methods have been developed for lakes globally, African lakes are typically underrepresented in training data, limiting the applicability of existing methods to the region. Hence, this study aimed to (1) assess the accuracy of existing and newly developed water quality band algorithms for East African lakes and (2) make satellite-derived water quality information easily accessible through a Google Earth Engine application (app), named LAndsat water QUality retrieval tool for east African lakes (LAQUA). We collated a dataset of existing and newly collected in situ surface water quality samples from seven lakes to develop and test Landsat water quality retrieval models. Twenty-one published algorithms were evaluated and compared with newly developed linear and quadratic regression models, to determine the most suitable Landsat band algorithms for chlorophyll-a, total suspended solids (TSS), and Secchi disk depth (SDD) for East African lakes. The three-band algorithm, parameterised using data for East African lakes, proved the most suitable for chlorophyll-a retrieval (R2 = 0.717, p < 0.001, RMSE = 22.917 μg/L), a novel index developed in this study, the Modified Suspended Matter Index (MSMI), was the most accurate for TSS retrieval (R2 = 0.822, p < 0.001, RMSE = 9.006 mg/L), and an existing global model was the most accurate for SDD estimation (R2 = 0.933, p < 0.001, RMSE = 0.073 m). The LAQUA app we developed provides easy access to the best performing retrieval models, facilitating the use of water quality information for management and evidence-informed policy making for East African lakes. [ABSTRACT FROM AUTHOR]

We compared the benefits of using extruded feed (EF), against pelleted feed (PF) to guide cage culture investments in Great Lakes. Three out of six cages in the same farm had fish that were fed EF and the other half, belonging to a different farm had fish that were fed PF. The diets were similar in crude protein, lipid and energy content. However, the fiber content in PF was 4 times higher than that of EF. The fish fed on EF grew better (438.0 ± 7.4 g) than the fish fed on PF (220.8 ± 2.9 g). The cost of production for EF was about 26% lower than for PF, primarily because of better feed utilization. The load of P and N for PF diet was 59% and 29% higher, respectively, than when EF was used. Therefore, EF feed delivered better economic gains with lower environmental impact than PF feed. [ABSTRACT FROM AUTHOR]

Cyanobacterial blooms are expanding around the globe in frequency and intensity. Using cultural models to unravel local meanings, this study explores how stakeholders (fishers, aquaculturalists, and regional experts) from the Nyanza Gulf of Lake Victoria understand cyanobacterial blooms and their impact on human health. The study also examines resource user and expert perceptions of how these blooms have impacted the livelihoods of fishers and aquaculturalists, and how regional experts have responded. Semi-structured interviews (35 total; fishers and aquaculturalists [25], experts [10]) were used to describe cultural models used by different groups. Multiple perceptions of cyanobacterial blooms and their impact on human health emerged, influenced by the social locations of study participants. With the burden of environmental degradation unequally allocated because of dynamic social constructs, these findings reveal the importance of improving the flow of information between those involved in the design and implementation of policies and those impacted by them. [ABSTRACT FROM AUTHOR]

The economic viability of tilapia cage culture in Lake Victoria was assessed using a profitability analysis model as the main decision support tool. One and five cages of 8 m3 (A), 62.5 m3 (B), and 471 m3 (C) were assessed. The break-even price (US$4.6 kg−1) for one cage of A appeared higher than the tilapia farm gate price in Kenya (US$3.5 kg−1), suggesting unprofitability of the venture. The decreased break-even price relative to increase in cage numbers showed economies of scale throughout the cage volume ranges. The longest payback period (PBP) for A (8 years) implied a risky venture. This was reaffirmed by an internal rate of return (IRR) of < 50% and negative Net present value (NPV) in the first two years of operations. The study affirmed the economic viability of operating large cage volumes (B or C) for Nile tilapia and for broader applicability to other Great Lakes. [ABSTRACT FROM AUTHOR]

Lake Victoria, like many other lakes in Africa, is affected by water hyacinth that reside in several bays for the majority of the year. The weed affects several economic activities of the local communities and denies revenue to the government from blue economic activities related to the lake. The present study examined the interaction of water hyacinth with biotic and abiotic factors and the efficiency of introduced weevils to better control this invasive weed. Water quality samples were collected and compared from the time of water hyacinth re‐emergence and sinking within the Winam Gulf of Lake Victoria. The present study was divided into three phases with an interval of 2 months. Water hyacinth was collected, and the damages resulting from the weevils to the hyacinth, as well as the number of weevils, was recorded and analysed. Fish samples were collected with experimental gill nets. The collected water samples was analysed for the aquatic plant nutrient ammonium, soluble reactive phosphorus, nitrates and nitrites. Data were analysed using R package. The results of the present study indicated that the weevils inhibited nutrient uptake by hyacinth by 17% within the first 4 weeks. The hyacinth subsequently increased the nutrient levels in the gulf by threefold after their decay and sinking. Weevils also increased the sinking rate of water hyacinth through the destruction of their petioles and leaves. One hundred and ninety‐four more fish were observed in the experimental nets during the weed infestation, compared to periods when the weed was absent within the gulf. The major conclusions were that water hyacinth impacts both biotic and abiotic factors, and that the weevils alone are unable to eradicate the weed. [ABSTRACT FROM AUTHOR]

We present the Multi-metric Index of Biotic Integrity methodological approach that allows for the ranking of major river catchments based on pollution status in the Kenyan portion of Lake Victoria, Africa. The study has a broader applicability to all of Lake Victoria, other African Great Lakes, and all lakes that have riverine discharge. The method presented utilizes water quality and environmental data, local knowledge, and pre-existing literature. The parameters considered were sampled from 2016 to 2018 during the dry season (July sampling) and the wet season (March sampling). Separation power of Mann-Whitney U test (p < 0.05) qualified 11 discriminant metrics for both macroinvertebrate and fish samples into the scoring system of 1, 3 and 5 in the formulation of final Multi-metric Index of Biotic Integrity methodological approach. Rivers in the northern section had lower Multi-metric Index of Biotic Integrity methodological approach scores, as compared to southern counterparts. The Multi-metric Index of Biotic Integrity methodological approach ranking herein was validated by community perceptions on pollution levels. River Nzoia catchment emerged as the most polluted, followed by River Yala, River Kuja, and Sondu-Miriu. Siltation, domestic washing, litter and refuse emerged as the main agents of pollution. Management authorities ought to reinforce a balanced utilization of the vital water resources to minimize future impacts, and promote catchment wide practices that ensure ecological health sustainability of the lake ecosystem. [ABSTRACT FROM AUTHOR]