Browsing by Author "Wegener, Anthony Marc"

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    Comparison of growth characteristics between the indigenous Oreochromis andersonii and the domesticated Oreochromis niloticus under experimental conditions
    (Stellenbosch : Stellenbosch University, 2016-03) Wegener, Anthony Marc; Brink, Danie; O’Neill, Bernadette; Stellenbosch University. Faculty of Agrisciences. Dept. of Animal Sciences.
    ENGLISH ABSTRACT: The increase in the world’s population and subsequent growth in demand for fisheries products is coinciding with the over-exploitation and decline of wild fish stocks. Fish however remains an important source of animal protein with more than half of the world’s population depends on fish as a source of animal protein. Aquaculture has become the fastest growing animal production sector with an average increase of 8 percent per annum over the past two decades. The Caprivi region, situated in the North Eastern section of Namibia has the second highest incidence of poverty in Namibia while its wetlands contains diverse habitats and contains approximately 86 resident fish species where habitat preference, breeding strategies, migration patterns and diet can vary inter-specifically. The Caprivi’s fishery plays an important role in that the majority of the population in this region depends on the fishery as a means of income, informal employment and food security. Aquaculture is promoted by the Namibian government as a supplement to the fishery in order to sustain livelihoods of the Caprivi region. Tilapia species has developed into the second most produced freshwater fish in the world, after the common carp (Caprinus carpio), with the domesticated Nile tilapia (Oreochromis niloticus) making up more than 80 percent of tilapia production. The Caprivi region plays host to a wide variety of indigenous tilapia species, including O. andersonii, O. macrochir, O. placidus, T. rendalli, and T. sparrmanii, of which the Three Spotted tilapia (O. andersonii) being the more common and targeted species in terms of the local fishery. Apart from promotion of the undomesticated indigenous O. andersonii for aquaculture purposes, the option remains also to introduce the domesticated and highly successful O. niloticus. Although beneficial in terms of aquaculture potential the introduction of O. niloticus though poses a significant risk of displacing various indigenous tilapia species such as O. andersonii, O.macrochir O.placidus, T.rendalli, and T.sparrmanii as well as affecting the biodiversity of the larger ecosystem. A comparative growth trial confirmed a significantly (P≤0.05) superior growth performance of O. niloticus over O. andersonii in terms of weight and length gain, with the undomesticated O. andersonii also displaying significantly higher variance (CV) for these traits. The growth curve of O.niloticus was isometric compared to the negative allometric growth of O.andersonii. Significant differences (P≤0.05) for moisture and crude lipid content were noted between species, where O.andersonii had higher crude lipid content and O.niloticus had higher moisture content. The proposed approach for developing tilapia aquaculture in the Caprivi region is to establish pilot projects to assess the economic feasibility for the production of the indigenous O.andersonii together with a cost-benefit analysis for the genetic improvement of the species. Furthermore to conduct a risk assessment associated with the introduction of O.niloticus into the Caprivi region with further decisions regarding the appropriate species to be based on the outcomes of the above assessments.