Browsing by Author "Mungai, Dan"

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    Ecological implications of Rastrineobola argentea (omena) fishery: A rapid assessment of bycatch diversity at Dunga Beach, Lake Victoria, Kenya
    (2022-06-01) Outa, Nicholas; Ogello, Erick; Okinyi, Walter; Mungai, Dan; Iteba, Jacob
    Rastrineobola argentea (omena) is the second most important species in the fisheries of Lake Victoria after Nile perch. However, its fisheries have negative impacts on the ecology of the lake especially because of the high numbers and diversity of bycatch resulting from the fishery. This study conducted a rapid assessment in Dunga beach in Kisumu, Kenya to identify and quantify the bycatch and to collect information on the fishermen’s perceptions of the bycatch from the omena fishery. All the boats reported bycatches of different species and different sizes. The bycatches comprised of Lates niloticus, Haplochromis spps, Clarias gariepinus, Protopterus aethiopicus, Synodontis. The smallest bycatch recorded was Haplochromis spp (3.3 cm; 3g) while the largest fish bycatch was Protopterus aethiopicus (1.5 m; 2.4 kg). Other bycatch recorded were freshwater shrimps and molluscs. 80% of the fishermen suggested the provision of alternative livelihoods as a measure to reduce the pressure on omena fishery while 12% recommended stricter rules on gears implemented. A total of 99% of the fishers reported that they do not return bycatch into the lake but rather sell them together with the main catch (omena). The implications of this on the ecological functioning of the lake is predicated on the negative impacts on the trophic interactions in the ecosystem.
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    The impacts of introduced species on lake ecosystems: A case of Lakes Victoria and Naivasha, Kenya.
    (2019-10-09) Outa, Nicholas; Mungai, Dan; Keyombe, James, Last
    Fish and other aquatic organisms have been introduced into new environments for various reasons. Provision of sports fishery, supplemental to stocks, to fill empty niches, control weeds, and disease vectors and even create a commercial fishery are some of the reasons why fish species are introduced into new ecosystems. Lake Victoria and Lake Naivasha in Kenya have seen several introductions as discussed in this paper. In Lake Victoria for example, some of the species introduced include Nile perch, Lates niloticus, Nile tilapia, Oreochromis niloticus, Tilapia zilii, and Oreochromis esclentus among others. The most successful introductions have been that of the Nile perch, Nile tilapia and water hyacinth. Lake Naivasha too has witnessed a number of introductions into its fisheries too. Some of the successful introductions into the lake are those of the Common carp, Cyprinus carpio, the largemouth bass, Micropterus salmoides, the Nile tilapia, O. niloticus and Louisiana red swamp crayfish, Procambarus clarkia. Aside from the fish species mentioned, some invasive plant species have also been introduced into these two lake ecosystems. Of notable success and impacts have been the water hyacinth, Eichhornia crassipes and Nile cabbage, Pistia stratiotes. These introductions have had both negative and positive impacts on the fisheries and the ecology of the two lakes. Some of the impacts have been predation on the native species by the introduced species like in the case of Nile perch and largemouth bass in Lake Victoria and Naivasha respectively. Competition for resources and hybridization with the native species has also been witnessed in the case of the tilapiines in the two lakes with undesirable results. Blockage of navigation routes caused by the invasive plants has been a major problem in the two lakes sometimes leading to massive postharvest losses by the fishermen. On the other hand, some introduced species have led to an increase in fish landings as well as utilization of the niches that were initially vacant within these ecosystems. It can therefore be concluded that introduced species often have more negative effects on the native species and therefore such introductions should be based on sound scientific research in order to minimize their effects within the new environments.
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    The status of research on Lake Victoria fisheries: Historical and current data on fisheries and the lake environment
    (2019-09-20) Outa, Nicholas; Mungai, Dan; Ogello, Erick
    Lake Victoria which is the second largest freshwater lake in the world supports a large population living around it through provision of food; fish and employment; both directly and indirectly. Due to its varied uses, human intervention within the lake and its catchment has caused several ecological changes in the recent years which have had profound effects on its resources. Historical and recent data within the lake show an enormous change in the diversity of the fish species as well as environmental and ecological changes. Some of the reasons cited for the changes in biodiversity within the lake are: the introduction of alien fish species like Nile perch (Lates niloticus) and Nile tilapia (Oreochromis niloticus) into the lake, habitat loss and the cultural eutrophication. Several research projects like Lake Victoria Management programme (LVEMP) and Lake Victoria Fisheries Organization (LVFO) have been formed to help address some of these problems with varied levels of success. There is therefore an urgent need for management measures based on sound scientific research to be taken in order to curb this loss of ichthyodiversity within the lake and to save the livelihoods of the people who are dependent on the lake. Owing to the importance of the lake to the livelihoods of the people around the lake and beyond, there is need for concerted effort by all stakeholders in trying to halt the degradation and other negative environmental and ecological changes within the lake. Ecosystem approach to conservation is the way forward in the management and sustainable utilization of the fisheries and other resources within the lake.