Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: This study investigated the “Effect of Phytogenic Feed Additives on Gonadal Development in Mozambique tilapia (Oreochromis mossambicus). Aquaculture remains the fastest growing animal food-producing sector and it is set to overtake capture fisheries as a source of food fish, and also to outpace population growth. This rapid growth can be attributed to the increasing demand for aquaculture products, and an urgent need for a sustainable food resource and the safe production of food. Globally, fish provides over 3.5 billion people with up to 15 percent of their average per capita intake of animal protein. The introduction of aquaculture to sub-Saharan African (SSA) took place during the 1940s and 1950s, and the main objectives were to improve nutrition in rural areas, allow for the diversification of activities to reduce the risk of crop failures, to generate additional income, and to create employment opportunities. Aquaculture was seen as a viable option for rural development in SSA, and substantial resources were invested to support its development. Poor results were however, recorded in terms of production and sustainability. Tilapia is the most widely cultured of all fish species farmed, and the second most important group of freshwater and brackish water fish after carps. Tilapia has all the necessary traits that makes it an excellent species to culture, but costefficient production is hampered by the animals attaining sexual maturity at a an early age, which then result in precocious breeding in aquaculture systems. The production of single-sex populations (i.e. all male) is a potential means to address the problem of precocious breeding, but the technologies used to establish single-sex populations are not readily available to resource-poor communities that farm with tilapia for food purposes. Phytochemicals, also known as phytoestrogens, are plant-derived compounds that structurally or functionally mimic mammalian estrogens that affect the sexual differentiation of fish. Phytochemicals occur in plants like Pawpaw (Carica papaya) and Moringa (Moringa oleifera). The study thus had a threefold objective. Firstly, the study investigated the potential of Pawpaw seed meal (P) and Moringa seed meal (M), as part of a commercial tilapia diet, to be used as endocrine disrupting compounds (EDC’s) to control the reproduction of sexually mature Mozambique tilapia (20-45g). Secondly, assess the potential of P and M to inhibit the attainment of sexual maturity in immature tilapia (2-8g). Finally, P and M to determine its influence on sexual differentiation of tilapia fry (9-12 days posthatch) to produce all-male populations. The study indicated that both P and M seeds contain bio-active chemicals that are capable of disrupting the gonad function, differentiation and sexual maturation of Mozambique tilapia. Sperm production was affected, evident in the degeneration of the testicular tissue samples. Egg production, ovulation and spawning were all affected, as evident in the difference in colour of the degrading eggs, as well as the absence of spawning. Ovo-testes were observed in cases where diets containing 10.0g P and 10.0g M /kg basal diet were fed. Eggs were observed in the ovaries of sexually immature fish, but spawning did not occur. The study also presents the first report on the isolation of Oleanolic acid in Moringa seeds. The evident of antifertility properties of both Pawpaw and Moringa seeds can be exploited to control or prevent reproduction of Mozambique tilapia in SSA aquaculture systems. This could be of particular importance to aquaculture development in rural areas of Sub-Saharan African countries, given the abundant year round availability of these compounds. Further studies are required to optimise the preparation of the experimental compounds; as well as determining the optimal inclusion level of the phytogenic compounds, as well as how their efficacy to manipulate the reproductive potential and ability of Mozambique tilapia are influenced by environmental factors such as water temperature. / AFRIKAANSE OPSOMMING: Akwakultuur is die vinnigste groeiende dierlike voedsel-sektor. Daar word verwag dat dit visserye sal oortref as ʼn bron van voedsel en dat groei in dié bedryf selfs die bevolkingsgroei sal verbysteek. Die vinnige groei in die sektor kan toegeskryf word aan die toenemende vraag na akwakultuur produkte en 'n dringende behoefte vir 'n volhoubare voedsel hulpbron, wat ook die veilige produksie van voedsel sal verseker. Wêreldwyd voed vis meer as 3.5 miljard mense en dra tot 15% van die gemiddelde hoeveelheid dierlike proteïen per kapita ingeneem, by. Die bekendstelling van akwakultuur in sub-Sahara Afrika (SSA) het gedurende die 1940's en 1950's plaasgevind, met die belangrikste doelwitte om voeding in landelike gebiede te verbeter, geleenthede vir diversifisering te skep wat die risiko van misoeste verminder, om bykomende inkomste te genereer en werksgeleenthede te skep. Akwakultuur is gesien as 'n lewensvatbare opsie vir die ontwikkeling van die landelike gebiede in SSA en aansienlike hulpbronne is belê om die ontwikkeling daarvan te ondersteun. Swak resultate is egter in terme van produksie en volhoubaarheid behaal. Tilapia is die mees algemene spesies wat gekweek word en is die tweede mees belangrike groep van varswater en brak water vis soesies, na Karp. Tilapia beskik oor al die nodige eienskappe wat dit ʼn uitstekende spesie vir voedselproduksie maak, maar koste-doeltreffende produksie daarvan word gekortwiek deur die feit dat die spesie seksuele volwassenheid op 'n vroeë ouderdom bereik, wat dan lei tot vroeg-rype teling en die gevolglike oorbevolking en swak groei van tilapia in ʼn akwakultuur sisteem. Die produksie van enkel-geslag bevolkings (d.i. slegs manlike vis) is ʼn potensiële oplossing vir dié probleme, maar die tegnologie wat gebruik word om enkel-geslag bevolkings te produseer is nie geredelik toeganklik vir hulpbron-arme gemeenskappe wat met Tilapia vir kosdoeleindes boer nie. Fitochemikalieë, anders ook bekend as fito-estrogene, is verbindings wat in plante voorkom en wat struktureel of funksioneel die werking van die natuurlike soogdier estrogene/androgene naboots, met die fitochemikalieë wat die seksuele differensiasie van vis beïnvloed. Fitochemikalieë kom in plante soos papaja (Carica papaya) en Moringa (Moringa oleifera) voor. Die studie het dus gepoog om die potensiaal van papaja saad meel (P) en Moringa saad meel (M), as deel van 'n kommersiële tilapia dieet, om as endokriene ontwrigters (EDC's) gebruik te word om die reproduksie van seksueel volwasse Mosambiek tilapia (20-45g) te beheer, om te voorkom dat onvolwasse tilapia (2-8g) geslagsrypheid te vroeg bereik en ook om die geslagsdifferensiasie van tilapia vingerlinge (9-12 dae na uitkom) te manipuleer om enkel-geslag (manlike) produksiegroepe te produseer. Die studie het aangedui dat beide papaja en Moringa sade bio-aktiewe chemikalieë wat die werking van die gonadotrofien hormone, geslagsdifferensiasie die stadium waarop Mosambiek tilapia geslagsrypheid bereik, kan beïnvloed. Spermproduksie is negatief beïnvloed, soos waargeneem in die degenerasie van die testisweefsel. Eierproduksie, ovulasie en die vrystelling van eiers is almal negatief beïnvloed, soos duidelik waargeneem in die kleurverskil (van normale eiers) van eiers wat ʼn mate van reabsorbsie aandui en die feit dat geen eiers vrygestel is nie. Ovo-testes is waargeneem in gevalle waar diëte met 10.0g papaja en / of Moringa / kg basale dieet gevoer is. Eiers is waargeneem in die eierstokke van seksueel onvolwasse vis, maar vrystelling het nie plaasgevind nie. Die studie is die eerste verslag oor die isolasie van Oleanoliese suur in Moringa sade. Die duidelike reproduksie-beperkende (anti-vrugbaarheid) eienskappe van beide papaja en Moringa sade kan benut kan word om reproduksie in Mosambiek tilapia te voorkom of te manipuleer in SSA akwakultuur stelsels. Dit is veral van besondere belang vir akwakultuur ontwikkeling in die landelike gebiede van SSA lande, gegewe dat beide sade regdeur die jaar geredelik beskikbaar is. Verdere studies word benodig om protokolle vir die voorbereiding van die eksperimentele verbindings te optimaliseer, sowel as die bepaling van die optimale insluitingsvlakke van die fitogeniese verbindings, asook hoe die doeltreffendheid van hierdie verbindings deur omgewingsfaktore soos water temperatuur beïnvloed word. / The University for Development Studies (UDS), Ghana, particularly Prof S.K. Nokoe, and Ghana Education Trust Fund (GETFund), for the initial financial support that enabled me to enrol for the programme. The Division of Aquaculture, together with the Postgraduate and International Office (Postgraduate Funding Section), Stellenbosch University (SU) for financial support during my studies.

Thesis (MPhil)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Tilapia is presumed to have a well-defined genetic mechanism of sex determination, but not all sex ratios are compatible with a monofactorial sex determination model. A theory of autosomal gene influence, as well as temperature sex determination (TSD) has been proposed in order to explain large variations in sex ratios. This study assessed the variation in progeny sex ratio in O. mossambicus as a basis for the application of YY male technology in the production of all-male progeny groups. Three populations of O. mossambicus were sampled that are representative of the geographical distribution of the species in Southern Africa. Progeny groups were produced from randomly selected parents and maintained at constant temperature during the labile period of sex differentiation. Variation in sex ratios between different families of the same strain as well as between different strains was calculated. No significant differences were observed in sex ratio between strains, though a significant intra-group variation was identified. This study identified both male and female-biased sex ratios. The data in general conform to a monofactorial sex determination model. Male-biased sex ratio observed in one strain can possibly be ascribed to temperature sex determination (TSD). This strain of O. mossambicus originated from an area with different annual temperature patterns and the possibility of TSD having an adaptive advantage is discussed. This thesis also presents the results of a program to produce monosex male tilapia through the application of the YY male technology in O. mossambicus. Viable XY female and YY male genotypes were produced. XY females sired progenies ranging from 68-94% male ofspring, while YY males sired a mean progeny of 94% male phenotypes. From these results it is concluded that YY male technology provide a viable method for the production of all-male progeny in O. mossambicus. Once available on a commercial scale, the technology can be made more reliable through the application of the appropriate selection methods. / AFRIKAANSE OPSOMMING: Tilapia spesies is oorwegend onderworpe aan ‘n goed gedefinieerde enkelfaktor model van genetiese geslagsbepaling, hoewel afwykings van sodanige geslagsbepalingsmodel soms waargeneem word. Die invloed van outosomale gene, sowel as omgewings temperatuur word voorgehou as verklaring van die waargenome variasies in geslagsverhoudings. Hierdie studie behels die evaluasie van variasie in geslagsdifferensiasie van O. mossambicus as basis vir die implementering van die YY manlike tegnologie vir die produksie van slegs-manlike nageslag groepe. Monsters is bekom van drie populasies van O. mossambicus verteenwoordigend van die geografiese verspreiding van die spesie in Suider Afrika. Nageslag groepe is geproduseer vanaf ewekansig gekose ouerpare en by ‘n konstante temperatuur gehuisves tydens die sensitiewe tydperk van geslagsdifferentiasie. Variasie in geslagsverhouding tussen verskillende families binne dieselfde subpopulasie sowel as binne verskillende populasies is bepaal. Geen betekenisvolle verskille is waargeneem in die geslagsverhouding tussen die verskillende populasies nie terwyl betekenisvolle verskille tussen families binne ‘n populasie waargeneem is. Die data voldoen aan ‘n enkelfaktor genetiese geslagsbepalingsmodel, met die uitsondering van een populasies waar ‘n moontlike omgewingsverwante geslagsbepalingseffek waargeneem is. Die tesis sluit ook in die resultate in van ’n program om YY-tegnologie in O. mossambicus te vestig ten einde manlike nageslag groepe te produseer. Funksionele vroulike XY- en manlike YY genotipes is ontwikkel. Die vroulike XY-genotipes het manlike nageslag groepe opgelewer wat wissel van 68%-94% manlik, terwyl manlike YY-genotipes nageslag groepe gelewer het wat gemiddeld 94% manlik was. Die resultate bevestig die lewensvatbaarheid van YY-tegnologie vir die kommersiële produksie van manlike nageslaggroepe in O. mossambicus.

A major obstacle facing the successful creation of an African aquaculture industry, based upon Oreochromids, is the irregular supply of good quality fish seed. There are several causative biological processes behind its irregular supply. The aim of this research was therefore to determine the basic requirements for the establishment and maintenance of a small breeding facility, for O. mossambicus. The goal was to make a unit that was simple and which could be easily replicated in rural, satellite aquaculture seed stations. The results obtained illustrate that a small reproduction unit can produce large quantities of healthy 90-day fry. Asynchronous hatching of the eggs and spawning asynchrony in female Oreochromis mossambicus are two elements which negatively affect uniformity in the fry produced. Typical fish seed production uses large ponds partitioned into breeding allotments or a series of breeding pools. While the earthen ponds provide a substrate in which a nest can be excavated, its presence is not required for mating success in the closely related O. niloticus (Linneaus 1758). Female mate choice, as well as apparent fecundity, according to nest size has been clearly recorded in related cichlids but no investigations have been made as to nest size and spawning synchrony in O. mossambicus. The main focus of this investigation was to ascertain whether O. mossambicus would accept artificial nest substitutes in preference to their own constructed ones and secondly, whether different alternatives would elicit different levels of acceptance. The observed results indicate a ready acceptance for artificial nest alternatives, with nest lip height being prioritised by the fish . The implications thereof are discussed in relation to the potential for optimization of breeding arenas for O. mossambicus by the provision of artificial nests whose dimensions satisfy both male and female preferences. In established communities, Oreochromis mossambicus display various complex and ritualised behaviours during stable and disruptive events. The aim of this research was primarily to produce a glossary of behaviours defining these interactions, particularly with reference to male-male behaviours. Three males and six females were allowed to acclimatise over one month, with various social groupings being established within the first few days. Results from this study illustrated not only a dynamic social structure, signaled via various chemosensory and visual methods, but also supported recent findings in apparent male-male courtship and the underlying ii causes. Furthermore, the observed male-male activity of the nestholder malesfirmly corroborate the current practice in aquaculture whereby only one male is allocated per breeding arena. The use of artificial incubation of Oreochromis spp. eggs has become widespread in high intensity fish seed production. Various types of incubator exist, and their selection is dependent on the specific attributes of the egg to be incubated. Currently available incubators are typically of a funnel (up-flow) or round bottomed (down-flow) design. Neither permits easy access to the eggs, which is particularly important when dealing with poor quality water as is typically found in rural areas. The aim of this study was to devise and test an easy-to-use incubator, applicable to rural seed production projects, which offers advantages over currently available incubator types. The final design, WETNURSE Type II, offered improved hatching rates over Type I, with a mean hatching success of 75%. While falling short of the desired 80% success rate (Rana 1986), the various other benefits provided by the design justify further optimization and testing. Three distinct populations of O. mossambicus, representing populations of inbred, randomly mated and genetically unknown (wild-caught) pedigree were analysed according to their food conversion efficiency (FCE). The intra- and inter-sample crosses were done with single males in order to produce half-sib progeny batches which allowed for the assessment of sire influences on the FCE of the progeny batches. The results show that the population of unknown pedigree is comparable to that of the randomly mating population, indicating the presence of sufficient genetic variation to permit further selection; the genetic contribution of the males to their respective progeny was insignificant in relation to that made by the female.