Browsing by Author "Alemayehu, Esayas"

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    Anthropogenic impacts on the contextual morphological diversification and adaptation of Nile tilapia (Oreochromis niloticus, L. 1758) in East Africa
    (Environmental Biology of Fishes, 2018) Dias Tibihika, Papius; Waidbacher, Herwig; Masembe, Charles; Curto, Manuel; Sabatino, Stephen; Alemayehu, Esayas; Meulenbroek, Paul; Akoll, Peter; Meimberg, Harald
    Nile tilapia occurs naturally in East Africa where it’s an economically important species. Many of the natural populations of Nile tilapia have been affected by anthropogenic activities including translocations, associated with programmes aimed at enhancing capture fisheries and aquaculture productivity. Using geometric morphometric analyses, we tested the hypothesis that such anthropogenic activities have augmented admixture among natural populations of Nile tilapia and influenced the geographical distribution of morphological variation within the species. Our expectation was that Nile tilapia shape divergent might be consistent with reportedly anthropogenic activities in nonnative environments. To test this hypothesis, we analyzed the shapes of 490 individuals from thirteen populations; three farms, six natives and four nonnative natural populations. Our analysis revealed that the most pronounced shape diversification was observed in seven populations; three nonnatives (Victoria, Kyoga and Sindi farm) and four natives (Albert, River Nile, George and Turkana). The features responsible for the observed morphotypes were mainly related to the orientation of the anterior region of the fish and may be due to diversifying selection in response to new environmental pressures (for nonnative populations), admixture or drift. Shape change in the nonnative high-altitude populations was unexpectedly conserved, suggesting recent introductions which may have not resulted in admixture or there was strong selection against change in the traits measured. On the other hand, the recorded morphotypic clusters explained the possible genetic link to their putative ancestral home. Our results were partially consistent with our prediction that the nonnative populations exhibited divergent morphotypes. We recommend further investigations with molecular genetics for followup of these findings.
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    Evaluation of willingness to pay toward improving water supply services in Sebeta town, Ethiopia
    (Journal of Water, Sanitation and Hygiene for Development, 2021) Eridadi, Hosea Mutanda; Inagaki, Yoshihiko; Alemayehu, Esayas; Kiwanuka, Moses
    Sebeta town is one of the rapidly growing towns in Ethiopia. Its closeness to Addis Ababa city has attracted industrial, urban development, and population growth. This development has created problems with drinking water shortages in the community. This study aimed at determining the household's willingness to pay (WTP) amount toward improving water supply services and analyzing the influencing factors of WTP. A contingent valuation (CV) technique was applied in quantifying the households' WTP and the influencing factors toward the program. The field observations, key informant interviews, and household questionnaire interviews from 250 respondents out of the targeted 280 were employed in collecting field data. Results from CV revealed that 66% of the households were WTP toward improving the water supply services beyond their current monthly water bills. Households were WTP about 20 Ethiopian Birr (ETB) above the average current water bill of 161 ETB. The binary logistic model results statistically demonstrated that independent variables of gender, age, marital status, education level, years in Sebeta, and average monthly income were significantly influencing the household's WTP at p = 0.01 and 0.05. This study provides vital hints for further research and baseline information for local administration and communities about the water supply in the area and holistic appropriation of water tariffs in line with government policy.
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    Molecular genetic diversity and differentiation of Nile tilapia (Oreochromis niloticus, L. 1758) in East African natural and stocked populations
    (BMC Evolutionary Biology, 2020) Tibihika, Papius Dias; Curto, Manuel; Alemayehu, Esayas; Waidbacher, Herwig; Masembe, Charles; Akoll, Peter; Meimberg, Harald
    The need for enhancing the productivity of fisheries in Africa triggered the introduction of non-native fish, causing dramatic changes to local species. In East Africa, the extensive translocation of Nile tilapia (Oreochromis niloticus) is one of the major factors in this respect. Using 40 microsatellite loci with SSR-GBS techniques, we amplified a total of 664 individuals to investigate the genetic structure of O. niloticus from East Africa in comparison to Ethiopian and Burkina Faso populations. Results: All three African regions were characterized by independent gene-pools, however, the Ethiopian population from Lake Tana was genetically more divergent (Fst = 2.1) than expected suggesting that it might be a different sub-species. In East Africa, the genetic structure was congruent with both geographical location and anthropogenic activities (Isolation By Distance for East Africa, R2 = 0.67 and Uganda, R2 = 0.24). O. niloticus from Lake Turkana (Kenya) was isolated, while in Uganda, despite populations being rather similar to each other, two main natural catchments were able to be defined. We show that these two groups contributed to the gene-pool of different non-native populations. Moreover, admixture and possible hybridization with other tilapiine species may have contributed to the genetic divergence found in some populations such as Lake Victoria. We detected other factors that might be affecting Nile tilapia genetic variation. For example, most of the populations have gone through a reduction in genetic diversity, which can be a consequence of bottleneck (G-W, < 0.5) caused by overfishing, genetic erosion due to fragmentation or founder effect resulting from stocking activities. Conclusions: The anthropogenic activities particularly in the East African O. niloticus translocations, promoted artificial admixture among Nile Tilapia populations. Translocations may also have triggered hybridization with the native congenerics, which needs to be further studied. These events may contribute to outbreeding depression and hence compromising the sustainability of the species in the region.