Aquaculture: Pathway to food security in Kenya...by Andrew Marriott and Odipo Osano

Photograph of the team and stakeholders

In late December we were successful in obtaining funding through a Newton International Links bid with the British Council. This project aims to investigate problems of food insecurity and the implications of anthropogenic pollutants for food safety, the impact on the health and nutritional quality of aquaculture farmed fish, and the potential of fisheries aquaculture to boost food security and sustainability in Lake Victoria, Kenya.

Having been successful in the bid, I was looking forward to working with fish again and using the knowledge gained from my years as a Marine Biologist at Bangor University. The project brings together my experiences working on fisheries aquaculture and from knowledge gained working within the Inorganic Geochemistry team in exploring micronutrients, pollution pathways and the associated problems of food security and nutrition in Aquaculture fish. 

This collaborative project involves the Inorganic Geochemistry team (IG) at BGS with our old friend Prof Odipo Osano from the School of Environmental Sciences at the University of Eldoret (UoE) with whom we have worked closely for over 4 years. This grant funded project also collaborates with Dr Tracey Coffey and Dr Sharon Egan from the School of Veterinary Science (University of Nottingham), and the experienced research team led by Dr Christopher Mulanda Aura at the Kenyan Marine Fisheries Research Institution (KMFRI) based in Kisumu, Kenya. 

Stakeholder discussions were hosted at KMFRI headquarters between the project team and aquaculture producers explaining how the project will address questions related to pollution pathways (Food Safety-human and ecological health), through studying problems associated with sedimentation rates in water from erosion, or changes in land-use and water quality, as well as the effects of toxic metals as drivers of antimicrobial resistance (AMR). Expanding on this, and linking to other BGS activities and interests of the Ministry for Agriculture, Livestock and Fisheries, data will be generated to understand the potential for aquaculture to address ‘hidden hunger’ (deficiencies of essential micronutrients for human and animal health). Questions came quick and fast from those attending, with the fisheries-licence holders and the cage-culture representative being extremely interested in what we were intending to do. However, transparency and open talks through public engagements such as this alleviated any concerns they may have had, and their subsequent assistance in locating sites and communicating with local cage managers proved invaluable .

Attention turned to the fieldwork, which was based on KMFRIs main research vessel R.V. Uvumbuzi (Discovery) based on the Winam Gulf in Kisumu. This allowed us direct access and quicker travel between sampling sites within the Winam Gulf to view and sample the intensity of aquaculture cages along the shores of Lake Victoria (Kenyan side).

Photograph of one of the larger aquaculture cages along the shores of Lake Victoria (Kenyan side)

Cage sizes ranged from a few meters (2x2) to the medium 6x4 meters up to the larger 20x20 meters and housing fish from a few thousand to over 20,000 for the larger 20x20 m cages. Most of the fish (Tilapia) are sold at local markets after growing for 6 months (plate size) or in the case of the larger cages (>10m) sold to merchants after growing for up to 8 months for re-sale as fillets..

Involving the representative for the aquaculture operators in the stakeholder meeting hosted by KMFRI, provided invaluable as they were able to help in the design of sampling locations, and assist in gaining the trust and co-operation of the managers of each cage site. With the local manager informed in advance of our visit, sampling fish from both within the cages, and from the wild went smoothly and efficiently.

Sampling involved all the experience of the project team. Water parameters such as pH, temperature, conductivity and dissolved oxygen were measured either directly from the vessel or from the small canoe brought along for closer inshore work. After measurements of the water were obtained, the process of collecting water samples from just below the surface (approx. 1m), and from depth, was completed using a niskin water sampler system. The collected water was then filtered using 0.45 um filters.

Water samples were observed to be slightly discoloured around the shores of Winam Gulf which is a possible indication of high sedimentation rates from land erosion. This colouration cleared when we moved further out to the main channel at Rusinga in the Lake. Finally the collection of a sediment sample was taken using the Van Veen Grab Sampler for both biogeochemical analysis in the UK, and benthic microbiological analysis by the team at KMFRI. Most of the sediment collected near the Winam Gulf area near the shore had a strong H2S aroma indicating possible eutrophic conditions in that area.

Photograph of Andy Marriott sub-sampling muscle tissue.

Fish were sampled both from the cages and also where possible from the wild, using fish locally caught by the local fishermen. Fish were processed on board the R.V. Uvumbuzi, and measurements were taken to record the biological data. Finally sub-samples of muscle tissue were taken and vacuum sealed for subsequent analysis of trace metals, and tissue for DNA extraction and Anti-Microbial Resistance studies.

After 3 long days working on the Lake, the water, sediment and fish tissue samples were finally off-loaded from the RV Uvumbuzi and transported to the School of Environmental Sciences (University of Eldoret). Here sediment samples were partially dried and excess water removed for transportation back to the Inorganic Geochemistry labs in the UK for ICP- MS analysis. Similarly, fish tissue will be measured for trace metals and DNA and AMR analyses at the School of Veterinary Science (University of Nottingham).

Water, fish tissue and sediment geochemistry data in addition to on-going studies by UoE and KMFRI will help to identify possible pollution pathways from anthropogenic activities, and sediment loading from erosion or changes in land-use for design of further investigation in the Winam Gulf and shores of Lake Victoria. Bio-geochemistry data from this and subsequent investigations will be invaluable to KMFRI in advising on the future siting of aquaculture cages to ensure food safety for human and ecological health. Given that ‘wild’ fish catches are unsustainable in Lake Victoria, aquaculture/farming of fish through sustainable methods is an important approach to food sufficiency and in addressing ‘hidden hunger’ along the shoreline of Lake Victoria and further inland.

Acknowledgements:

I would like to thank the Newton International Links programme and the British Council for funding the project. I would also like to thank the BGS-ODA programme and Center for Environmental Geochemistry for financial support and technical expertise.