Browsing by Author "Harald Meimberg"

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Exploring the morphological dynamics of Nile tilapia (Oreochromis niloticus Linn. 1758) in Victoria Nile as depicted from geometric morphometrics
(BMC Zoology, 2023-11-23) Papius Dias Tibihika; Manuel Curto; Harald Meimberg; Cassius Aruho; George Muganga; Jerome Sebadduka Lugumira; Victoria Tibenda Namulawa; Margaret Aanyu; Richard Ddungu; Constantine Chobet Ondhoro; Tom Okurut
Background Various anthropogenic activities continue to threaten the fish biodiversity of the East African water bodies such as the Victoria Nile. Although the Victoria Nile is a significant source of livelihood for human populations, the biology and ecology of Nile tilapia in this ecosystem remain understudied with little or no information on the morphology of the fish given varying and immense anthropogenic activities. Here, we use geometric morphometrics to examine the morphology/shape variations of Nile tilapia populations in Victoria Nile to gain insights into their current ecological state. Results Our results indicate unexpectedly smaller Nile tilapia body weights in Victoria Nile than in L. Victoria. Despite this, nearly all the populations displayed a relative condition factor (Kn) of greater ≥1 suggesting a healthy stock. How- ever, two populations, LMF and VN_Bukeeka demonstrated Kn values of less than one (< 1). We also report that some Upper and Lower Victoria Nile populations display morphological similarities. Apart from L. Albert, Nile tilapia populations from Lakes Victoria and Kyoga are morphologically divergent from the riverine ones. We note that Nile tilapia from Nalubale Dam Reservoir is morphologically distinct from the close neighbouring Victoria Nile populations which are likely allied to the influence of the Nalubale Hydroelectric power dam as a barrier. Conclusion Nile tilapia’s morphological variation appears to be influenced by various anthropogenic disturbances notably, over fishing, hydroelectric power dams, and fish translocational history in Uganda. Management should enforce regulatory frameworks to avert human-mediated activities as these are likely to compromise the sustainability of the sheries. Further studies are required to follow these populations with molecular genetics and environmental data to gain a deeper understanding of the sh species for informed sustainable management and conservation options.
Introgressive hybridization levels of Tilapiine species in Lake Victoria basin, Kenya inferred from microsatellite and mitochondrial DNA genotyping based on next-generation sequencing
(Conservation Genetics, 2023-09-27) Gerald Kwikiriza; Thapasya Vijayan; Papius Dias Tibihika; Manuel Curto; Gerold Winkler; Juliet Kigongo Nattabi; John Kariuki; Harald Meimberg
Despite their high abundance and species richness, tilapiines have been compromised by various factors especially over fishing, climate change, and uncontrolled sh transfers and introductions. Fish introductions have negatively impacted native tilapiine populations through competition, predation, hybridization, and introgression compromising their genetic integrity. The hybridization levels of different tilapiines in the Lake Victoria basin remain relatively understudied. The study utilized nuclear microsatellite and mitochondrial DNA (mtDNA) genetic markers to investigate hybridization signals and compare the genetic diversity of different tilapiines in Lake Victoria, Kenya, using next-generation sequencing. Low levels of hybridization from Oreochromis niloticus into other Oreochromis species were detected by Bayesian clustering analysis and principal coordinate analysis (PCoA). The results contribute to the need for conservation measures for these sh species.
Morphometric Variations of Nile Tilapia (Oreochromis niloticus) (Linnaeus, 1758) Local Strains Collected from Different Fish Farms in South Western Highland Agro-Ecological Zone (SWHAEZ), Uganda: Screening Strains for Aquaculture
(Fishes, 2023-04-20) Gerald Kwikiriza; Mourine J. Yegon; Nelson Byamugisha; Apulnal Beingana; Faith Atukwatse; Alex Barekye; Juliet K. Nattabi; Harald Meimberg
Despite the global contribution of aquaculture as an important pillar for food and nutritional security, its rapid growth has been hampered by inadequate and poor-quality seed due to inbreeding, hybridization of related stocks, and poor-quality broodstock. Phenotypic and genotypic characterization of Nile tilapia in natural water bodies of Uganda has been studied but research gaps remain on the morphometric characterization of farmed O. niloticus in Uganda, which hinders selective breeding initiatives. This study characterized O. niloticus from various farmers in Uganda’s Southwestern Highland Agro-Ecological Zone using their morphometric traits. In this study, 8 morphometric traits were taken on each of the 258 fish samples collected with at least 30 samples sampled from each pond system in the zone. The morphometric data generated were analyzed using multivariate analysis. In order to delineate the populations from the different ponds, Discriminant Function analysis (DFA) was performed on the dataset and distribution plots generated to test on the purity of the strains. There were significant differences in the morphometric traits among the populations with the Victoria fish population having the highest standard length while the Kyoga population had the highest weight. Morphometric characterization grouped the fish into three clusters, indicative that fish farms in the zone possibly had different sources of fish seed. The condition factor, which is a measure of wellbeing of the fish, showed that all the populations displayed an isometric growth which is indicative of the fish growing in length as it is in weight. The results of this study provide evidence that local O. niloticus from different farms display differences in body shape as a result of using fish seed from different sources. This aspect can be applied in selective breeding programs after establishing the genetic structure of the farmed Nile tilapia stock.