The population of Sub-Saharan Africa is growing at an estimated 2.7% per year, more than twice that of South Asia and Latin America. This growth rate will lead to a doubling of the region’s population by 2050, which poses a significant challenge with respect to food security.
Capture fisheries in the whole of Africa are well above aquaculture production, which contrasts sharply with the global situation (FAO, 2020)—since 2013, over half of the seafood for direct human consumption is sourced from aquaculture. Contrary to world fisheries, which are flatlining, African wild catch is still increasing, but the share of aquaculture in production of seafood has tripled since the year 2000. In parallel, per capita fish consumption in sub-Saharan Africa is very low, generally below 5 kg ind-1 y-1. Out of the three nations bordering Lake Victoria, only Uganda consumes over 10 (10-20) kg ind-1 y-1 (FAO, 2020).
The decline of capture fisheries in the Great Lakes due to over-fishing and other factors has been ongoing for several decades (Ogutu-Ohwayo et al, 1997), and catches of Nile perch (Lates niloticus) and Nile tilapia (Oreochromis niloticus) in Lake Victoria have decreased markedly since the 1990s (Katunzi, 2019).
The dual challenges of collapse of capture fisheries and population growth—the population of the Kenyan catchment of Lake Victoria is expected to double by 2050, in line with the rest of Sub-Saharan Africa—mean that aquaculture is one of the potential solutions to allow expanding human populations to have access to food security over the next thirty years and beyond.
Tilapia, due to its high growth rate, well-established husbandry, and low trophic status, shows great promise as a high-quality protein source, and Lake Victoria has appropriate conditions for its cultivation. However, in order to ensure that aquaculture expansion in this region is achieved in a sustainable manner, a development framework is required to address the challenges of environmental sustainability and ecosystem carrying capacity.
In order to illustrate the underlying issues, and in particular the challenges in the implementation of the Ecosystem Approach to Aquaculture (EAA - Soto et al, 2008), taking into account ecological sustainability, social balance, and harmonization of multiple uses, a well-tested framework for zoning and carrying capacity assessment is being applied in Lake Victoria. The rationale is that models of this kind can be used to support industry development and help managers make informed decisions about sustainable expansion of aquaculture.
Approach
The framework used for carrying capacity assessment builds on a combination of various models, which together are used to understand the different components of the system (Fig. 3). These include individual growth models, local-scale carrying capacity models, farm footprint models for both organic and inorganic waste, models for land use in order to partition nutrient loading, and spatial analysis tools.
This complex framework is being developed as part of the Sustainable Activities in Water Areas (SAWA) project, developed by Kenya, which aims to build an aquaculture governance framework that improves decision-making and addresses the challenges of multiple lake uses in the Kenyan part of Lake Victoria.
In parallel to the modelling framework, a full stakeholder consultation and engagement programme is developed within SAWA. The results obtained from the natural sciences components of the work will helpto inform factually-based discussions and promote consensus among aquaculture businesses, fishers, management agencies, and the wider community.
The application of the Ecosystem Approach to Aquaculture for the Kenyan area of Lake Victoria will create conditions for industry growth, contemplating both artisanal cultivation practiced by local communities associated to Beach Management Units (BMU) and more sophisticated operations that include full vertical integration from farm to fork.
Results and discussion
A mass balance for individual growth modelling for Tilapia, using the well-tested AquaFish model (e.g. Ferreira et al, 2015) is shown in Fig. 2. The model will be tuned for Lake Victoria, where production of market-sized tilapia takes longer than in Thailand or China, which may be related to feed quality or to other husbandry aspects. The model forms the basis for local-scale modelling of tilapia farms, which in turn will be used to drive simulations of organic deposition and enable the assessment of ecological carrying capacity.
Fieldwork and stakeholder consultation showed that both local communities and larger businesses are committed to work within SAWA to provide data and improve the knowledge base essential for the successful application of EAA to Lake Victoria, and fully expect to benefit from the project outcomes. A frequent stakeholder concern was to ensure that the results of SAWA have the necessary buy-in from policy makers as a condition for success.
We hope that the implementation of a successful aquaculture framework for the Kenyan water area, taking into account the uses of the associated catchment, will exemplify how this participative governance model can be extended to the lake as a whole, given that transboundary systems must be managed holistically.
References
FAO (Food and Agriculture Organization of the United Nations), 2020. The state of world fisheries and aquaculture (SOFIA). FAO, Rome, 224 pp.
Ferreira, J.G., L. Falconer, J. Kittiwanich, L. Ross, C. Saurel, K. Wellman, C.B. Zhu, P. Suvanachai, 2015. Analysis of production and environmental effects of Nile tilapia and white shrimp culture in Thailand. Aquaculture, 447, 23-36.
Katunzi, E.F.B., 2019. A review of Lake Victoria Fisheries. In Johnson, T.C. and Odada, E.O. Eds. The limnology, climatology and paeloclimatology of the East African lakes. CRC Press, 664 pp.
Ogutu-Ohwayo, R., Hecky, R.E., Cohen, A.S. et al., 1997. Human impacts on the African Great Lakes. Environmental Biology of Fishes 50, 117–131. https://doi.org/10.1023/A:1007320932349
Soto, D., Aguilar-Manjarrez, J. & Hishamunda, N. (eds). 2008. Building an ecosystem approach to aquaculture. FAO/Universitat de les Illes Balears Expert Workshop. 7–11 May 2007, Palma de Mallorca, Spain. FAO Fisheries and Aquaculture Proceedings. No. 14. Rome, FAO. 2008. 221p.