M.Sc. / Hydrocynus vittatus, commonly known as the tigerfish, plays an important role in riverine ecology. It is a top predator which roams the open waters of most larger river systems in southern Africa. Their presence in a freshwater ecosystem has a dramatic impact on the fish community structure. It is known that dams and weirs have a negative effect on the migration of the tigerfish. It is also evident that tigerfish do not occur in certain areas in some of the rivers where they have been present historically. The Olifants and Letaba Rivers in the Kruger National Park (KNP) are two of a few rivers within South Africa where tigerfish do occur. The KNP represents the edge of the most southern distribution of tigerfish in southern Africa. It was therefore expected that the tigerfish do not function optimal in the Olifants and Letaba Rivers as they are subjected to waters with high concentrations of silt and low flow which influences migration and successful breeding. Breeding migrations does however take place during the summer months after which the tigerfish returns to the Massingire Dam in Mozambique to avoid the colder winter temperatures in the rivers. Gonad development coincide with the yearly summer rainfall patterns. A deviation of the expected 1:1 male:female sex ratio to favour the males was experienced in both rivers, which may be the result of over population. Females were found to grow to a larger size than the males and were extremely fecund. Although H. vittatus is believed to be mainly piscivorous, other food items such as invertebrates, played an important role in the diet of small and large tigerfish in both the Olifants and Letaba Rivers. Invertebrates were mostly preyed upon which implies that optimal feeding conditions for the tigerfish does not prevail in these systems and that they have to adapt to satisfy their feeding requirements. Tigerfish is more abundant in the Olifants than in the Letaba River. The overall growth performance or phi prime (4)) values for H. vittatus in the Olifants River was determined and compares well to the overall growth performance of tigerfish in the Okavango River and Lake Kariba. However the maximum length calculated for tigerfish in the Olifants River (Lco = 52.40 cm ) is smaller than the Lco values (56.06 cm) for the Okavango River. The mortality rate of tigerfish in the Olifants River exceeds those in the Letaba River which means that the life expectancy is longer in the Letaba as opposed to the Olifants River. Successful artificial spawning revealed some of the secrets of the reproduction strategy of this species. Tigerfish has semi pelagic eggs, are very small (0.65 mm), negatively buoyant and slightly adhesive for bentic and epibiotic incubation, and it is expected that tigerfish would spawn in open water, on a sandy substrate in the vicinity of aquatic vegetation. First hatching took place at 22h 30 min after fertilization. Vertical movement of the larvae lasts for two days, which allows for downstream movement and dispersement of the larvae. It was found that tigerfish replace their teeth on a regular basis as they grow larger. Transition from conical to functional dentition takes place 45 days after hatching. Replacement of sets of teeth occurs during all phases of its lifespan. It is a quick proses of three to six days during which all teeth are replaced in both the upper and lower jaws.

The first of a series of mass mortalities of Nile crocodiles in the Olifants and Letaba rivers in the Kruger National Park (KNP) was reported in the winter of 2008. The present study investigated the levels and possible effects on eggshell thickness of inorganic elements and organic pollutants in Nile crocodile eggs from these rivers, and comparing them with eggs from a reference crocodile farm and a reference dam inside the KNP. The egg contents were analyzed for chlorinated organic compounds and brominated flame retardants. Eggshells and egg contents were analyzed for inorganic elements. The elemental concentrations in the eggshells and contents were low when compared with previous studies. The highest concentrations were found in the eggs from the reference crocodile farm. The eggs from the reference dam and the crocodile farm had thicker shells, and the eggs from the Olifants and Letaba rivers had thinner shells. Not all eggs in a female develop at the same rate, while eggshell formation presumably occurs at the same time for all eggs. As a result, the elemental profile of egg contents may differ between eggs of the same clutch, but less so for the shells. Weak or no associations were found between the elemental concentrations of the content and eggshells and eggshell thinning. A possible organic pollutant–induced eggshell thinning effect was found. The compounds found were not at levels that could have caused the mortalities, but may affect the sex ratios through endocrine disruption. Further studies are therefore required. / Thesis (M.Sc (Environmental Science))--North-West University, Potchefstroom Campus, 2011.

The first of a series of mass mortalities of Nile crocodiles in the Olifants and Letaba rivers in the Kruger National Park (KNP) was reported in the winter of 2008. The present study investigated the levels and possible effects on eggshell thickness of inorganic elements and organic pollutants in Nile crocodile eggs from these rivers, and comparing them with eggs from a reference crocodile farm and a reference dam inside the KNP. The egg contents were analyzed for chlorinated organic compounds and brominated flame retardants. Eggshells and egg contents were analyzed for inorganic elements. The elemental concentrations in the eggshells and contents were low when compared with previous studies. The highest concentrations were found in the eggs from the reference crocodile farm. The eggs from the reference dam and the crocodile farm had thicker shells, and the eggs from the Olifants and Letaba rivers had thinner shells. Not all eggs in a female develop at the same rate, while eggshell formation presumably occurs at the same time for all eggs. As a result, the elemental profile of egg contents may differ between eggs of the same clutch, but less so for the shells. Weak or no associations were found between the elemental concentrations of the content and eggshells and eggshell thinning. A possible organic pollutant–induced eggshell thinning effect was found. The compounds found were not at levels that could have caused the mortalities, but may affect the sex ratios through endocrine disruption. Further studies are therefore required. / Thesis (M.Sc (Environmental Science))--North-West University, Potchefstroom Campus, 2011.

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: South Africa's system of socio-economic development planning is complex and ine ective. There are many regulatory authorities involved, often with unclear responsibilities and inadequate procedures of implementing objectives. Planning for development in South Africa needs to take various factors into account. Economic growth is pursued, while social imbalances are addressed and the environment is protected against unreasonable damage. The term Sustainable Development is an important concept in the vision of many of the regulating authorities, however, the implementation of sustainability is di cult. This study considers an approach which aligns activities in a specifi ed region to the vision and objectives of the applicable regulatory authorities, as an alternative to achieving objectives strictly through enforcing regulations. This thesis developed an integrated evaluation model which can be used to evaluate the alignment of a small-scale farm to the visions and objectives of certain regulatory authorities. Four small-scale farms in the Letaba catchment of the Limpopo Province were used as a case study to be evaluated against national and regional development visions. On a national level the National Development Plan (NDP), the National Framework for Sustainable Development (NFSD), the Integrated Sustainable Rural Development Strategy (ISRDS) and the principles of Water Allocation Reform (WAR) were regarded. For regional categorisation, the relevant municipal Integrated Development Plan (IDP), Spatial Development Framework (SDF), Local Economic Development (LED) plan and the applicable Catchment Management Strategy (CMS) were considered. The Letaba catchment area has speci c development constraints regarding water. For this reason, the impact the four farms have on the water of the region was evaluated in addition to their alignment with regional development visions. The hydrological evaluations were performed through the use of the Soil and Water Assessment Tool. Hereby it was determined whether objectives of development planning were realistic in terms of water availability. It was established that the location of a farm is a determining factor of the impact it has on the catchment area's water supply. The developed Integrated Evaluation Model combined all the visions and objectives of the mentioned strategic documents to speci cally assess the contribution a small-scale farm makes. The evaluation results provide insight into the alignment of activities to the ideals of a region and can be useful when formulating actions to reach a common vision. Small-scale farms are well-aligned to the objectives of WAR, the CMS and ISRDS. The farms have a limited contribution to the ideals of the NDP and NFSD and results against the IDP, the SDF and the LED di er considerably for each farm. Furthermore, the results of the farms' alignment with regional objectives do not correspond to the hydrologically ideal locations. Therefore, the development of small-scale farming should take hydrological information into consideration. The Integrated Evaluation Model proves to be valuable, understandable and applicable to evaluate the alignment of small-scale farms to the visions of regulatory authorities. / AFRIKAANSE OPSOMMING: Suid-Afrika se sisteem van beplanning vir sosio-ekonomiese ontwikkeling is ingewikkeld en one ektief. Daar is verskillende regulatoriese owerhede betrokke wat maklik aanleiding gee tot onsekerheid ten opsigte van verantwoordelikhede asook tot onvoldoende benaderings tot implementering. Om ontwikkeling in Suid-Afrika suksesvol te laat geskied, moet verskeie faktore inaggeneem word. Behalwe vir die strewe na ekonomiese groei, moet sosiale agterstande gelyktydig aangespreek word en moet hierdie ontwikkeling van so 'n aard wees dat die omgewing nie onnodige skade lei nie. Volhoubaarheid is 'n gemeenskaplike ideaal van die meeste partye betrokke by die beplanning van Suid-Afrika se ontwikkeling. Die implementering van hierdie oogmerk is egter onduidelik. Hierdie studie oorweeg 'n benadering wat alle handelinge in 'n bepaalde gebied in ooreenstemming bring met die visie en doelwitte van die toepaslike regulatoriese owerhede. Hierdie benadering word as 'n alternatief gestel teenoor 'n benadering om doelwitte slegs deur regulasies te bereik. Hierdie tesis het 'n Geïntegreerde Evalueringsmodel ontwikkel wat die mate waartoe 'n klein plaas 'n bydrae maak tot die visie en doelwitte van regulatoriese owerhede meet. Vier kleinskaalse boerderye in die Letaba Opvangsgebied in Limpopo was ondersoek as 'n gevallestudie. Hierdie plase is geëvalueer teen nasionale- en streeksontwikkelingsvisies. Op 'n nasionale vlak is die Nasionale Ontwikkelings Plan (NOP), die Nasionale Raamwerk vir Volhoubare Ontwikkeling (NRVO), die Geïntegreerde Volhoubare Landelike Ontwikkelings Strategie (GVLOS) en die waardes van die Water Toekenning Hervorming (WTH) beskou. Ten opsigte van streeksontwikkeling, is die betrokke munisipale Geïntegreerde Ontwikkelings Plan (GOP), die Ruimtelike Ontwikkelings Raamwerk (ROR), Plaaslike Ekonomiese Ontwikkeling (PEO) plan en die gepaste Opvangsgebied Bestuurs Plan (OBP) inaggeneem. Water is 'n beperkende faktor tot ontwikkeling in die Letaba opvangsgebied. Omrede, word die vier plase se impak op die watertoestand van die gebied bepaal, sowel as die bydrae tot die visie van die regulatoriese owerhede. 'n Opstelling van die studie-area is gemaak met die Soil and Water Assessment Tool ten einde hidrologiese a eidings te maak. Hierdeur is bepaal of die visies en doelwitte soos gestel deur die beplanningsdokumente vir ontwikkeling, realisties is ten opsigte van die waterbeskikbaarheid. Die studie het bevestig dat die ligging van 'n plaas 'n bepalende faktor is tot die plaas se uitwerking op die gebied se water. Die ontwikkelde Geïntegreerde Evalueringsmodel kombineer die visies en doelwitte van die bogenoemde strategiese dokumente om die bydrae van 'n klein plaas te meet. Die evalueringsresultate verskaf insigte rondom die ooreenstemming van plase teenoor die visie van 'n streek en kan nuttig gepas kom wanneer spesi eke aksies beplan word om 'n gemeenskaplike doelwit te bereik. Kleinskaalse boerdery is in lyn met die doelwitte soos bepaal deur die OBP, GVLOS en WTH. Die bydrae wat die plase ten opsigte van die NOP en NRVO se ideale maak is egter beperk. Verder verskil die resultate grootliks vir elke plaas ten opsigte van die bydrae gelewer tot die visies van die GOP, ROR en PEO. Gewensde resultate ten opsigte van bydrae tot ontwikkelingsvisies het nie ooreengestem met die liggings wat aanbeveel is deur die hidrologiese studie nie. Dus moet hidrologiese inligting inaggeneem word tydens besluitneming vir die ontwikkeling van kleinskaalse boerdery. Die Geïntegreerde Evalueringsmodel bied waarde, is toeganklik en is toepaslik om kleinskaalse boerdery te meet tenoor die visies van regulatoriese owerhede.