Lake Victoria:: The water hyacinth (Eichhornia crassipes [MART.] SOLMS), its socio-economic effects, control measures and resurgence in the Winam gulf

The aquatic weed Eichhornia crassipes [MART.] SOLMS was introduced in Lake Victoria from Rwanda via the Kagera River by the activities of man. After originally infesting Lake Victoria 14 (Uganda), it eventually spread into the Winam gulf, where its proliferation was spectacular, resulting in an enormous public outcry. The aim of this study was to find out how a beach/bay covered by a weed carpet affected the life of a lakeshore community, if there were any seasonal changes in carpet sizes and to establish if the water hyacinth is a friend or an enemy. Surveys were conducted in selected beaches between June 1995 and November 1999. When surveys were complete, it became clear that this weed is nomadic, except in lagoons and beaches that had little external interference. The open waters remained generally clear due to constant wave action. Interviews conducted on selected beaches/bays indicated that weed carpets impacted both positively and negatively, i.e. they disrupted fishing activities, transport, irrigation, water treatment. enhanced breeding grounds for vectors of human diseases, impacted on biodiversity and had become a source of raw materials for making furniture, paper and artefacts. After successful biological control by the Kenya Agricultural Research Institute (KART), resurgence and succession were observed. The impact of water hyacinth on the life of the lakeshore communities in the Winam gulf is serious and needs to be quantified. Further research is necessary to establish whether this weed is an enemy or a friend of the lakeshore communities.