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With increasing demand for improved farmed Nile tilapia (Oreochromis niloticus) fish seed, there is heightened demand for quality and proven broodstock by hatchery operators throughout the country and in the East African region. Uganda, fortunately, is endowed with vast natural Nile tilapia (Oreochromis niloticus) stocks in lakes Albert, Edward and George, as well as in Albert Nile River. To aquaculturally benefit from the different attributes of different stocks/strains, it is important to establish the existing strains in a manner that is phenotypically discernible where such differences are apparent. In this study, we used a suite of morphological traits to identify strains of Nile tilapia among 425 individuals sampled from the four major water bodies, lakes – Albert, Edward-George, Kyoga and Victoria. Morphological variation was investigated using multivariate approaches including principal component analysis, discriminant analysis and cluster analysis of 22 morphometric characters. These analyses indicated that there was high morphological variation among the different populations of Nile tilapia and the fish could be grouped into their respective sampled areas based on these morphological differences. Most of the variation (86.97%) was associated with the fish body size, the peduncle length and the interorbital distances. Findings imply that there are four major Nile tilapia strains in Ugandan waters that will be subjected to aquaculture performance evaluation before being used in the genetic improvement programme to produce improved Nile tilapia fish broodstock/seed for use in fish farming. Differences among populations may reflect genetic differences and/or environmental factors.
Keywords: Morphometrics, Oreochromis niloticus, strain identification