Comparison of growth characteristics between the indigenous Oreochromis andersonii and the domesticated Oreochromis niloticus under experimental conditions

Wegener, Anthony Marc (2016-03)

Thesis (MSc)--Stellenbosch University, 2016.

Thesis

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.

AFRIKAANSE OPSOMMING: Die toename in die wêreld se bevolking en die daaropvolgende groei in die vraag vir die vissery produkte is wat saamval met die oorbenutting en agteruitgang van wilde visbronne. Fish is egter 'n goeie bron van dierlike proteïen en meer as die helfte van die wêreld se bevolking is afhanklik van vis as 'n bron van dierlike proteïen. Akwakultuur het die vinnigste groeiende diereproduksie sektor met 'n gemiddelde styging van 8% per jaar oor die afgelope twee dekades. Die Caprivi-streek, geleë in die afdeling Noord Oos van Namibië het die tweede hoogste voorkoms van armoede in Namibië terwyl die vleilande bevat diverse habitats en bevat ongeveer 86 inwoner visspesies waar habitat voorkeur, teling, migrasie patrone en dieet inter-spesifiek kan wissel . Vissery die Caprivi se is baie belangrik, want meer as die helfte van die bevolking in die streek is afhanklik van die vissery as 'n middel van inkomste, informele indiensneming en voedselsekuriteit. Die groeiende vraag na proteïen bronne kan tevrede wees deur akwakultuur van mak spesies soos O.niloticus, tans die gewildste gekweek mak tilapia spesies. Maar sodra dit ontsnap dit sal 'n negatiewe impak op die veerkragtigheid en produktiwiteit van buitelandse ekosisteem en sal die druk op en die moontlikheid van plaaslike uitwissing van verskeie vis en ander akwatiese spesies te Aan die ander kant O.andersonii is inheems aan die Caprivi, algemeen verkies deur plaaslike gemeenskappe en het potensieel goeie akwakultuur eienskappe. Afgesien van die bevordering van die produksie van die undomesticated inheemse spesie, die opsie moet ook nog 'n hoogs mak tilapia spesies vir akwakultuur doeleindes stel om te help om goedkoop goeie gehalte proteïen na omliggende gemeenskappe sowel as gemak visvang druk op wilde visbronne en te bewaar biodiversiteit. Maar die spesie hou 'n beduidende risiko van die verskuiwing verskeie inheemse tilapia spesies soos O. andersonii, O.macrochir O.placidus, T.rendalli en T.sparrmanii asook wat die biodiversiteit van die groter ekosisteem as dit ontsnap. Albei spesies ervaar lineêre groeikoerse met die mak spesies (O.niloticus) met aansienlik hoër gemiddelde daaglikse groei in terme van gewigstoename en lengte gewin, as wilde spesies (O.andersonii). O.andersonii aan die ander kant het beter koëffisiënt van variasie van die gemiddelde daaglikse groei as O.niloticus. Isometriese groei is gerapporteer deur die O.niloticus terwyl O.andersonii ervaar negatiewe allometric groei. Die toestand faktore dui beide spesies is in 'n gesonde toestand. Beduidende verskille vir voginhoud en ru lipied inhoud is opgemerk tussen spesies, waar O.andersonii het hoër ru lipied inhoud en O.niloticus het hoër voginhoud. Die stel benadering tot die ontwikkeling akwakultuur in die Caprivi is deur die ontwikkeling van loodsprojekte kweek O.andersonii en terselfdertyd bydra navorsing makmaak van die inheemse O.andersonii. Verder ondersoek die evaluering van risikobestuur op alle moontlike gevolge / risiko's wat verband hou met O.niloticus ontsnap in die omliggende rivierstelsels. Sodra die O.andersonii loodsprojekte is ten volle funksionele en al relatiewe risiko-ontledings afgehandel is, na gelang van die verskillende uitkomste kan projekte te loods op kweek O.niloticus in die

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