Fish Diversity, Community Structure, Feeding Ecology, and Fisheries of Lower Omo River and the Ethiopian Part of Lake Turkana, East Africa
| dc.contributor.advisor | Getahun, Abebe(PhD) | |
| dc.contributor.author | Wakjira, Mulugeta | |
| dc.date.accessioned | 2018-07-23T11:54:57Z | |
| dc.date.accessioned | 2023-11-09T04:22:12Z | |
| dc.date.available | 2018-07-23T11:54:57Z | |
| dc.date.available | 2023-11-09T04:22:12Z | |
| dc.date.issued | 2016-06 | |
| dc.description.abstract | Ethiopia has a freshwater system in nine major drainage basins which fall into four ichthyofaunal provinces and one subprovince. Omo-Turkana Basin, spanning considerable geographic area in southwestern Ethiopia and northern Kenya, essentially consists of Omo River (also known as Omo-Gibe) and Lake Turkana. The entire of Omo River and about 1.3% of the lake (ca. 98 km2) lie within Ethiopia. The Ethiopian part of the basin generally lacks comprehensive study and proper scientific documentation on its ichthyofaunal diversity, ecology and fisheries. This study was thus undertaken to address these gaps. Data were obtained using various methods over a period of two years, and analyzed using various computations, univariate tests and multivariate methods. Thirty-one fish species were identified from lower Omo River and the Ethiopian part of Lake Turkana, with some new records, from the present collections. Omo River system was found to be more species rich than Lake Turkana but poorer in abundance. The basin’s extent of ichthyofaunal diversity within the limit of Ethiopia was specifically addressed, for which an artificial identification key was prepared. Annotated checklist for the native species was provided for the entire basin. Composition of the most important species (total index of relative importance, IRI > 94%) was essentially similar for the river and the lake, but differed in the relative importance of each species. Cluster analysis and principal component analysis (PCA) produced distinct habitat-associated species patterns across the riverine and lacustrine environments. The Ethiopian part of Lake Turkana community consisted of 18 fish species, of which two-thirds were species of highest relative importance. The lower Omo River community consisted of 13 species of largely lower IRI. Ionic concentration measured as total dissolved solids (TDS) was found to be the key environmental factor determining fish community structure in lower Omo-Turkana sub-basin. Feeding habits of eight selected fish species from the Ethiopian part of Lake Turkana have been identified and described. Although 11 major prey groups were identified for all species, only 7 prey categories viz. aquatic insects, phytoplankton, macrophytes, fish, zooplankton, detritus and prawn were the most important contributors to the fishes’ dietary variations. Fish, aquatic insects, phytoplankton and zooplankton constituted the most diversified prey categories. The eight species ranged in the generalist-specialist feeding strategy spectrum with Synodontis schall (Bloch & Schneider, 1801) being the most generalist feeder, while Oreochromis niloticus (Linnaeus, 1758) was the most specialist feeder. Each fish species consisted of subpopulations with various dietary niche width contributions to the species’ overall feeding strategy. Ontogenetic and seasonal dietary variations were observed for all the fish species examined except for S. uranoscopus whose diet virtually remained constant across fish size and seasons. The eight examined fish species formed two trophic guilds, with the mainly piscivorous group consisting of Schilbe uranoscopus Rüppell, 1832, Bagrus bajad (Forsskål, 1775) and Lates niloticus (Linnaeus, 1758), and the mainly planktivorous group consisting of ii S. schall, Distichodus nefasch (Bonnaterre, 1788), Alestes baremoze (Joannis, 1835), Citharinus citharus (Geoffroy St. Hilaire, 1809) and O. niloticus. The number of guilds and dietary items that defined guild structures did not vary on seasonal and non-seasonal situations; however, a change in guild organization was observed. The computed Horn’s dietary niche overlap indices corroborated categorization of the examined fish species according to their prime dietary resource utilization. The river and the lake supported small-scale gill net fisheries that provided livelihood, income and employment to three major fisher-categories. Fisheries value chain was developed and major issues arising out of the chain components were addressed, fishers’ perceptions about the resource condition and management status were identified and discussed. In order to sustain fisheries socioeconomic contributions to livelihoods of the local people, the government in particular the regional state should take a prime responsibility to address the major socioeconomic issues arising out of the fisheries value chain analysis and issues related to resource management. Particularly, conflict of the Ethiopian fishers with the rival Turkana tribe fishers of Kenya should be properly addressed as it could jeopardize any attempt of resource management effort. Keywords: Annotated checklist, community structure, diversity, Ethiopia, feeding habits, fish, Lake Turkana, Omo River, small-scale fisheries, socioeconomics, total dissolved solids, trophic guild. | en_US |
| dc.identifier.uri | http://etd.aau.edu.et/handle/123456789/9814 | |
| dc.language.iso | en | en_US |
| dc.publisher | Addis Ababa University | en_US |
| dc.subject | Annotated Checklist | en_US |
| dc.subject | Community Structure | en_US |
| dc.subject | Diversity | en_US |
| dc.subject | Ethiopia | en_US |
| dc.subject | Feeding Habits | en_US |
| dc.subject | Fish | en_US |
| dc.subject | Lake Turkana | en_US |
| dc.subject | Omo River | en_US |
| dc.subject | Small-scale Fisheries | en_US |
| dc.subject | Socioeconomics | en_US |
| dc.title | Fish Diversity, Community Structure, Feeding Ecology, and Fisheries of Lower Omo River and the Ethiopian Part of Lake Turkana, East Africa | en_US |
| dc.type | Thesis | en_US |
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