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Understanding the Impacts of Water Inflow Changes on the Fishes of Lake Turkana, Kenya


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Lake Turkana, Kenya is an understudied desert lake that receives over 90% of its inflow from the Omo River in Ethiopia. The volume and patterns of inflow from this river influence the lake’s chemistry and productivity, as well as the availability of habitat and the breeding migrations of its fishes. Lake Turkana is at the precipice of large-scale changes in ecological function due to climate change and economic development along the Omo River, including the construction of massive dams and irrigation projects. Upstream development will reduce the volume of water entering the lake and dampen the lake’s ecologically crucial seasonal flood pulse. These changes will almost certainly impact the lake’s fisheries at a time when they are becoming increasingly important to local livelihoods and national food security. This dissertation considers how the lake’s fish communities, which have not been well studied since the 1980’s, will respond to upstream development. Using data from satellite altimetry and local fisheries organizations, this study showed that water levels and their fluctuations are key drivers of fisheries productivity in the system. Using geographic information systems, water levels were shown to alter the distribution of habitat types and seasonal flood pulses to determine the extent of productive dynamic littoral habitat in the lake. Stable isotope analysis and a breeding vulnerability index for the top fishery species in the system showed that while some species of economic importance are ecologically flexible (e.g. Oreochromis niloticus. Lates niloticus), others (e.g. Tilapia zillii, Labeo horie) are highly sensitive to changes in habitat availability and food web structure. Lastly, a synthesis of published food web models for African lakes showed that altering the magnitude of water level fluctuations of these lakes has implications for their productivity, fish diversity, and the complexity, efficiency and connectivity of their food webs. Taken together, these studies suggest that upstream development will have extensive negative consequences for Lake Turkana and its fisheries. Although recommendations are made regarding minimizing impacts to the lake, more research must be conducted to comprehensively inform water resource management in the region.
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... Kolding (1989;1992) also provided an update on the ichthyofaunal list that focused mainly on the lake's fisheries. Recent studies on the ichthyofaunal diversity of the Omo River and Lake Turkana on the Ethiopian side have been undertaken as part of Joint Ethio-Russian Biological Expedition (JERBE) and PhD projects (Golubtsov and Darkov, 2008;Prokofiev and Golubtsov, 2013;Gownaris, 2015;Wakjira, 2016;Wakjira and Getahun, 2017). ...
... A snapshot update on the status of the fish stocks was conducted by Muška et al. (2012) in the open water of the central part of the lake through a hydroacoustic survey and supplementary gill net investigation. Around this time, Gownaris (2015), Gownaris et al. (2015) and Gownaris et al. (2017) collected data on the lake's food web and water quality as part of her PhD study from 2011 to 2013. From the limited data that do exist, many ecologically unique and scientifically interesting characteristics have emerged, such as the intimate ties between the lakes' drastic water level fluctuations and its fauna (e.g., tilapia production: Kolding, 1993a; primary productivity: Tebbs et al., 2019; overall fisheries catch: Gownaris et al., 2017), the semi-saline chemistry of the system, the low flora and fauna diversity for its size, a mid-scattering layer of small endemic characins (Alestes spp.), and intermittent phenomenal peaks in production of tilapia (Oreochromis niloticus) (Kolding, 1993a). ...
Lake Turkana, located in northwestern Kenya and south-western Ethiopia, is Africa’s fourth largest lake and the world’s largest permanent desert lake. The lake lies in a closed basin and its limnology, ecology, and fisheries are driven by seasonal cycles of flooding from the Omo River, which provides more than 90% of the lake’s inflow. Lake Turkana is a unique ecosystem and is home to at least 79 fish species (12 endemic), the world’s largest remaining population of Nile crocodile, and hundreds of resident and migratory bird species. The lake has considerable fisheries resources that contribute to food security, employment, and the general wellbeing of local communities. Lake Turkana is also the least studied of the Great Lakes of Africa, due to its remoteness, the absence of necessary scientific infrastructure, and the scarcity of trained personnel in the field of aquatic sciences and fisheries in the region. Here, we present a review based on the available literature and on expert discussions and surveys to synthesize current knowledge, research gaps, and opportunities for increasing our knowledge on this unique ecosystem. Our literature review showed that there is a marked lack of interdisciplinary and applied research on Lake Turkana, and that much of the work published on the system (63.3%) focuses on previous geological periods rather than the current state of the ecosystem. We highlight four critical steps that need to be taken to improve research into this system: local capacity building, consistent monitoring and data sharing, sustainable financing, and strengthened collaborative networks.
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The Length-Weight relationship (LWR), condition factor and feeding habits of Synodontis schall (Bloch and Schneider, 1801) were studied over a 24-month period from January, 2009 to December, 2010. A total number of 635 specimens comprising of 329 males and 306 females with the size range of 6.1-30.40 cm and the mean of 12.04 ± 0.11cm were studied. The weight ranged from 53.0-864g with the mean of 57.71 ± 2.26g. The LWRs for the females, males and combined sexes had r-values of 0.9333, 0.9308 and 0.9411respectively. The mean condition factor K was 2.874, 2.838 and 2.855; regression coefficient b 2.5290, 2.4977 and 2.6749 for the females, males and combined sexes respectively. Out of the 635 stomachs examined for food items, 153 (24.09%) were empty while 482 (75.91%) contained wide range and varying quantities of food items indicating that S.schall in River Benue is Omnivorous.
Technical Report
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Located in the “cradle of mankind” of the East African Rift Valley, Lake Turkana is distinguished as both the world’s largest permanent desert lake and alkaline water body. With a surface area of about 7,560 km2, Lake Turkana is a highly pulsed, variable system as a result of its closed-basin nature, arid surroundings, and its strong dependence on River Omo for the majority of its inflow, which originates as rainfall over the Ethiopian highlands. In this article we describe the lake’s unique ecosystem and associated vicissitudes, diverse habitats and incredible biodiversity, and ecosystem services. Although parts of the lake and lower Omo Delta have been zoned as an international biosphere reserve, Lake Turkana and the region are facing immense threat from anthropogenic activities. A combination of external factors (hydropower dams, irrigation schemes, climate anomalies) and internal drivers (demography, economic growth) will strongly impact the Lake Turkana basin over the next decade. In turn, this will have significant negative consequences on resource productivity and the wellbeing of local communities.