Post-impoundment population dynamics of non-native common carp Cyprinus Carpio in relation to two large native cyprinids in Lake Gariep, South Africa
- Authors: Winker, Henning
- Date: 2011
- Subjects: Cyprinidae -- South Africa -- Gariep Dam Carp -- South Africa -- Gariep Dam Fish populations -- South Africa -- Gariep Dam Fishes -- Physiology -- South Africa -- Gariep Dam Barbus aeneus -- South Africa -- Gariep Dam Mudfishes -- South Africa -- Gariep Dam Freshwater fishes -- South Africa -- Gariep Dam
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5311 , http://hdl.handle.net/10962/d1005156
- Description: To contribute to the understanding of the invasion biology of common carp Cyprinus carpio in southern Africa, this thesis investigated the life history, relative abundance, long-term population demographics and trophic niche utilisations of non-native common carp C. carpio in relation to two endemic cyprinids, Orange River mudfish Labeo capensis and smallmouth yellowfish Labeobarbus aeneus in South Africa‟s largest impoundment, Lake Gariep. The growth zone deposition rates in astericus otoliths of the three species were validated as biannual for C. carpio and as annual for L. capensis and L. aeneus, which allowed for reliable estimation of lengths-at-age upon which growth, age-at-maturity and mortality rates could be estimated. Cyprinus carpio exhibited fast growth, matured relatively early at two years of age and attained a maximum age of seven years. Labeo capensis grew significantly slower, but attained older ages of up to 12 years. Females showed notably delayed maturation at approximately six years of age. The life history parameter estimates for L. aeneus were similar to those of L. capensis. These species-specific life history characteristics contributed to a substantially higher population growth potential of C. carpio compared to L. capensis and L. aeneus. Delta-lognormal and delta-gamma Generalized Linear Models (GLMs) were used to analyse patterns of relative abundance of L. capensis, L. aeneus and C. carpio. The application of these GLMs was necessary to account for large proportions of zeros and strong skewness in the catch-per-unit-effort (CPUE) from experimental gillnet and fisheries-dependent angler surveys. Confidence intervals around predicted abundance indices were obtained through the development of a generalised parametric bootstrap procedure. The resulting standardised abundance indices were coupled with results from analysis of stable isotope ratios of fish tissues and potential food resources and revealed that C. carpio was mainly confined to soft-bottom habitats, where it predominantly foraged on benthic invertebrates. Labeo capensis was abundant in a wide range of benthic habitats and was consumed basal food resources such as detritus. Labeobarbus aeneus was found to feed mostly on pelagic zooplankton. There were no significant interspecific differences in trophic niche space, suggesting limited resource competition among the three species. Standardised historical and contemporary gillnet CPUE data indicated slow population growth rates of L. capensis and L. aeneus during the first ten years postimpoundment, but showed high biomass levels some four decades after impoundment. These results could be corroborated by stochastic age-structured production model (ASPM) simulations. In contrast to the two endemic species, the gillnet CPUE of C. carpio showed a clear „boom and bust‟ pattern, which, based on ASPM simulations, could be best explained by increased food availability during the first five years postimpoundment, followed by suboptimal conditions thereafter. Together, these results provided evidence that the establishment of the C. carpio population did not prevent the slow but successful long-term establishment of the two large endemic cyprinids. Both endemic fishes revealed specialised feeding within the impoundment.
- Full Text:
- Date Issued: 2011
- Authors: Winker, Henning
- Date: 2011
- Subjects: Cyprinidae -- South Africa -- Gariep Dam Carp -- South Africa -- Gariep Dam Fish populations -- South Africa -- Gariep Dam Fishes -- Physiology -- South Africa -- Gariep Dam Barbus aeneus -- South Africa -- Gariep Dam Mudfishes -- South Africa -- Gariep Dam Freshwater fishes -- South Africa -- Gariep Dam
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5311 , http://hdl.handle.net/10962/d1005156
- Description: To contribute to the understanding of the invasion biology of common carp Cyprinus carpio in southern Africa, this thesis investigated the life history, relative abundance, long-term population demographics and trophic niche utilisations of non-native common carp C. carpio in relation to two endemic cyprinids, Orange River mudfish Labeo capensis and smallmouth yellowfish Labeobarbus aeneus in South Africa‟s largest impoundment, Lake Gariep. The growth zone deposition rates in astericus otoliths of the three species were validated as biannual for C. carpio and as annual for L. capensis and L. aeneus, which allowed for reliable estimation of lengths-at-age upon which growth, age-at-maturity and mortality rates could be estimated. Cyprinus carpio exhibited fast growth, matured relatively early at two years of age and attained a maximum age of seven years. Labeo capensis grew significantly slower, but attained older ages of up to 12 years. Females showed notably delayed maturation at approximately six years of age. The life history parameter estimates for L. aeneus were similar to those of L. capensis. These species-specific life history characteristics contributed to a substantially higher population growth potential of C. carpio compared to L. capensis and L. aeneus. Delta-lognormal and delta-gamma Generalized Linear Models (GLMs) were used to analyse patterns of relative abundance of L. capensis, L. aeneus and C. carpio. The application of these GLMs was necessary to account for large proportions of zeros and strong skewness in the catch-per-unit-effort (CPUE) from experimental gillnet and fisheries-dependent angler surveys. Confidence intervals around predicted abundance indices were obtained through the development of a generalised parametric bootstrap procedure. The resulting standardised abundance indices were coupled with results from analysis of stable isotope ratios of fish tissues and potential food resources and revealed that C. carpio was mainly confined to soft-bottom habitats, where it predominantly foraged on benthic invertebrates. Labeo capensis was abundant in a wide range of benthic habitats and was consumed basal food resources such as detritus. Labeobarbus aeneus was found to feed mostly on pelagic zooplankton. There were no significant interspecific differences in trophic niche space, suggesting limited resource competition among the three species. Standardised historical and contemporary gillnet CPUE data indicated slow population growth rates of L. capensis and L. aeneus during the first ten years postimpoundment, but showed high biomass levels some four decades after impoundment. These results could be corroborated by stochastic age-structured production model (ASPM) simulations. In contrast to the two endemic species, the gillnet CPUE of C. carpio showed a clear „boom and bust‟ pattern, which, based on ASPM simulations, could be best explained by increased food availability during the first five years postimpoundment, followed by suboptimal conditions thereafter. Together, these results provided evidence that the establishment of the C. carpio population did not prevent the slow but successful long-term establishment of the two large endemic cyprinids. Both endemic fishes revealed specialised feeding within the impoundment.
- Full Text:
- Date Issued: 2011
Life history and population dynamics of invasive common carp, Cyprinus carpio, within a large turbid African impoundment
- Winker, A Henning, Weyl, Olaf L F, Booth, Anthony J, Ellender, Bruce R
- Authors: Winker, A Henning , Weyl, Olaf L F , Booth, Anthony J , Ellender, Bruce R
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124898 , vital:35708 , https://doi.10.1071/MF11054
- Description: Common carp (Cyprinus carpio) is one of the world’s most widely introduced and established freshwater fishes (Casal 2006). The species is considered to be one of the eight most invasive freshwater fishes (Lowe et al. 2000) and worldwide, it accounts for most of the records of successful establishments and adverse ecological effects (Casal 2006; Kulhanek et al. 2011). This invasive success suggests that feral C. carpio is equipped with a set of adaptable life history attributes that allow it to successfully colonise a wide range of habitats (Koehn 2004; Zambrano et al. 2006; Britton et al. 2007). Where feral C. carpio occurs in high densities, it is often perceived as an invasive pest species (Sivakumaran et al. 2003; Brown and Walker 2004; Koehn 2004) because it can have severe impacts on habitat heterogeneity and biodiversity by increasing water turbidity through its bottom feeding behaviour, increasing nutrient availability, decreasing benthic and macrophyte density and diversity, altering zooplankton assemblages and decreasing endemic fish abundance (Zambrano et al. 2001; Khan 2003; Kulhanek et al. 2011). Within south-east Australia, for example, C. carpio comprises the largest proportion of the ichthyobiomass in the continent’s largest river system – the Murray–Darling Basin (Gehrke et al. 1995). As a consequence, serious concerns about its threat to endemic freshwater species (Koehn 2004) have prompted several of the most recent investigations into its life history (e.g. Sivakumaran et al. 2003; Smith and Walker 2004; Brown et al. 2005). Other potential threats posed also include competition with indigenous species and the spread of diseases and parasites (Dudgeon et al. 2006). In South Africa, for example, Asian tapeworm Bothriocephalus acheilognathi is now widely distributed in seven river systems and has infected eight novel cyprinid hosts due to the translocation of infected by C. carpio from a centralized aquaculture facility (Stadtlander et al. 2011).
- Full Text:
- Date Issued: 2011
- Authors: Winker, A Henning , Weyl, Olaf L F , Booth, Anthony J , Ellender, Bruce R
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124898 , vital:35708 , https://doi.10.1071/MF11054
- Description: Common carp (Cyprinus carpio) is one of the world’s most widely introduced and established freshwater fishes (Casal 2006). The species is considered to be one of the eight most invasive freshwater fishes (Lowe et al. 2000) and worldwide, it accounts for most of the records of successful establishments and adverse ecological effects (Casal 2006; Kulhanek et al. 2011). This invasive success suggests that feral C. carpio is equipped with a set of adaptable life history attributes that allow it to successfully colonise a wide range of habitats (Koehn 2004; Zambrano et al. 2006; Britton et al. 2007). Where feral C. carpio occurs in high densities, it is often perceived as an invasive pest species (Sivakumaran et al. 2003; Brown and Walker 2004; Koehn 2004) because it can have severe impacts on habitat heterogeneity and biodiversity by increasing water turbidity through its bottom feeding behaviour, increasing nutrient availability, decreasing benthic and macrophyte density and diversity, altering zooplankton assemblages and decreasing endemic fish abundance (Zambrano et al. 2001; Khan 2003; Kulhanek et al. 2011). Within south-east Australia, for example, C. carpio comprises the largest proportion of the ichthyobiomass in the continent’s largest river system – the Murray–Darling Basin (Gehrke et al. 1995). As a consequence, serious concerns about its threat to endemic freshwater species (Koehn 2004) have prompted several of the most recent investigations into its life history (e.g. Sivakumaran et al. 2003; Smith and Walker 2004; Brown et al. 2005). Other potential threats posed also include competition with indigenous species and the spread of diseases and parasites (Dudgeon et al. 2006). In South Africa, for example, Asian tapeworm Bothriocephalus acheilognathi is now widely distributed in seven river systems and has infected eight novel cyprinid hosts due to the translocation of infected by C. carpio from a centralized aquaculture facility (Stadtlander et al. 2011).
- Full Text:
- Date Issued: 2011
The general and emotional development of a sample of South African children in residential care
- Authors: Wills, Nicolene
- Date: 2011
- Subjects: Children -- Institutional care -- South Africa , Child psychopathology -- Residential treatment -- South Africa , Children -- Services for -- South Africa , Child welfare -- South Africa , Child care services -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:9856 , http://hdl.handle.net/10948/1578 , Children -- Institutional care -- South Africa , Child psychopathology -- Residential treatment -- South Africa , Children -- Services for -- South Africa , Child welfare -- South Africa , Child care services -- South Africa
- Description: The main aim of this study was to explore and describe the general and emotional development of a sample of South African children between the age of five and eight years in residential care. More specifically, the study aimed to explore and describe the general level of development of a sample of children in residential care; to explore and describe the development of a sample of children in residential care in six areas of development; and to describe the emotional wellbeing of children in residential care. A non-probability, purposive sampling method was applied as the participants were comprised of children between the ages of 5 and 8 years housed at the residential care facility. The sample consisted of 11 children. The multiple case study method was used to achieve the aim of the study, using both qualitative and quantitative data. The quantitative data consisted of scores obtained from the administration of the Griffiths Mental Development Scales - Extended Revised (GMDS-ER). The qualitative data was obtained from the Human Figure Drawing (HFD), participants’ scholastic progress reports, case reports from the residential care facility and clinical observations during the assessment period. The data was analysed according to thematic analysis. The results highlighted the pervasiveness of delays in all domains of child development of children housed in residential care, specifically that of language, social and emotional development. An important finding of the study was that decrements in these domains of development underpinned delays in the other domains of development since they form the foundation of learning and relating to the world. The study served to emphasize the importance of consistent developmental assessment in order to ascertain whether these children present with developmental delays and, if so, to xv identify which areas of development are most affected. Information from the developmental assessments could assist in the early identification of developmental delays and allow for individually tailored interventions to overcome such delays.
- Full Text:
- Date Issued: 2011
- Authors: Wills, Nicolene
- Date: 2011
- Subjects: Children -- Institutional care -- South Africa , Child psychopathology -- Residential treatment -- South Africa , Children -- Services for -- South Africa , Child welfare -- South Africa , Child care services -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:9856 , http://hdl.handle.net/10948/1578 , Children -- Institutional care -- South Africa , Child psychopathology -- Residential treatment -- South Africa , Children -- Services for -- South Africa , Child welfare -- South Africa , Child care services -- South Africa
- Description: The main aim of this study was to explore and describe the general and emotional development of a sample of South African children between the age of five and eight years in residential care. More specifically, the study aimed to explore and describe the general level of development of a sample of children in residential care; to explore and describe the development of a sample of children in residential care in six areas of development; and to describe the emotional wellbeing of children in residential care. A non-probability, purposive sampling method was applied as the participants were comprised of children between the ages of 5 and 8 years housed at the residential care facility. The sample consisted of 11 children. The multiple case study method was used to achieve the aim of the study, using both qualitative and quantitative data. The quantitative data consisted of scores obtained from the administration of the Griffiths Mental Development Scales - Extended Revised (GMDS-ER). The qualitative data was obtained from the Human Figure Drawing (HFD), participants’ scholastic progress reports, case reports from the residential care facility and clinical observations during the assessment period. The data was analysed according to thematic analysis. The results highlighted the pervasiveness of delays in all domains of child development of children housed in residential care, specifically that of language, social and emotional development. An important finding of the study was that decrements in these domains of development underpinned delays in the other domains of development since they form the foundation of learning and relating to the world. The study served to emphasize the importance of consistent developmental assessment in order to ascertain whether these children present with developmental delays and, if so, to xv identify which areas of development are most affected. Information from the developmental assessments could assist in the early identification of developmental delays and allow for individually tailored interventions to overcome such delays.
- Full Text:
- Date Issued: 2011
Adoption and sustained use of M-Commerce to improve efficacy of construction SMMEs
- Authors: Williams, Zenande
- Date: 2011
- Subjects: Construction industry , Mobile commerce , Small business , Computer-assisted instruction , Interactive videos
- Language: English
- Type: Thesis , Masters , MCom (Information Systems)
- Identifier: vital:11125 , http://hdl.handle.net/10353/528 , Construction industry , Mobile commerce , Small business , Computer-assisted instruction , Interactive videos
- Description: E-commerce has been said to bring value to businesses by improving business efficiency and effectiveness and thus providing business with a competitive advantage through the potential benefits that it offers (Cloete, Courtney & Fintz, 2002). However, despite the potential benefits that e-commerce can offer, the adoption of B2C e-commerce in South African construction SMMEs is low and this is due to the challenges associated with e-commerce (Vaithanathan, 2010; Uzoka, Shemi & Seleka, 2007; Love & Irani, 2004; Anumba & Ruikar, 2002). These e-commerce challenges include: high implementation costs, lack or poor infrastructure, inadequate resources, low use of e-commerce by suppliers and consumers, lack of access to e-commerce, computer illiteracy, deficiency in understanding the potential benefits of e-commerce and security concerns (Vaithanathan, 2010; Uzoka, Shemi, & Seleka, 2007; Mensah, Bahta, & Mhlanga, 2005; Cloete, Courtney, & Fintz, 2002). Therefore, due to these e-commerce challenges, construction SMMEs do not exploit the business advantages that e-commerce offers. In order to assist South African construction SMMEs in their efforts to improve their business effectiveness and efficiency through commercial technologies.
- Full Text:
- Date Issued: 2011
- Authors: Williams, Zenande
- Date: 2011
- Subjects: Construction industry , Mobile commerce , Small business , Computer-assisted instruction , Interactive videos
- Language: English
- Type: Thesis , Masters , MCom (Information Systems)
- Identifier: vital:11125 , http://hdl.handle.net/10353/528 , Construction industry , Mobile commerce , Small business , Computer-assisted instruction , Interactive videos
- Description: E-commerce has been said to bring value to businesses by improving business efficiency and effectiveness and thus providing business with a competitive advantage through the potential benefits that it offers (Cloete, Courtney & Fintz, 2002). However, despite the potential benefits that e-commerce can offer, the adoption of B2C e-commerce in South African construction SMMEs is low and this is due to the challenges associated with e-commerce (Vaithanathan, 2010; Uzoka, Shemi & Seleka, 2007; Love & Irani, 2004; Anumba & Ruikar, 2002). These e-commerce challenges include: high implementation costs, lack or poor infrastructure, inadequate resources, low use of e-commerce by suppliers and consumers, lack of access to e-commerce, computer illiteracy, deficiency in understanding the potential benefits of e-commerce and security concerns (Vaithanathan, 2010; Uzoka, Shemi, & Seleka, 2007; Mensah, Bahta, & Mhlanga, 2005; Cloete, Courtney, & Fintz, 2002). Therefore, due to these e-commerce challenges, construction SMMEs do not exploit the business advantages that e-commerce offers. In order to assist South African construction SMMEs in their efforts to improve their business effectiveness and efficiency through commercial technologies.
- Full Text:
- Date Issued: 2011
On the design and monitoring of photovoltaic systems for rural homes
- Authors: Williams, Nathaniel John
- Date: 2011
- Subjects: Photovoltaic cells , Dwellings -- Power supply
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10516 , http://hdl.handle.net/10948/1308 , Photovoltaic cells , Dwellings -- Power supply
- Description: It is estimated that 1.6 billion people today live without access to electricity. Most of these people live in remote rural areas in developing countries. One economic solution to this problem is the deployment of small domestic photovoltaic (PV) systems called solar home systems (SHS). In order to improve the performance and reduce the life cycle cost of these systems, accurate monitoring data of real SHSs is required. To this end, two SHSs typical of those found in the field were designed and installed, one in a rural area of the Eastern Cape of South Africa and the other in the laboratory. Monitoring systems were designed to record energy ows in the system and important environmental parameters. A novel technique was developed to correct for measurement errors occurring during the utilization of pulse width modulation charge control techniques. These errors were found to be as large as 47.6 percent. Simulations show that correction techniques produce measurement errors that are up to 20 times smaller than uncorrected values, depending upon the operating conditions. As a tool to aid in the analysis of monitoring data, a PV performance model was developed. The model, used to predict the maximum power point (MPP) power of a PV array, was able to predict MPP energy production to within 0.2 percent over the course of three days. Monitoring data from the laboratory system shows that the largest sources of energy loss are charge control, module under performance relative to manufacturer specifications and operation of the PV array away from MPP. These accounted for losses of approximately 18-27 percent, 15 percent and 8-11 percent of rated PV energy under standard test conditions, respectively. Energy consumed by loads on the systems was less than 50 percent of rated PV energy for both the remote and laboratory systems. Performance ratios (PR) for the laboratory system ranged from 0.38 to 0.49 for the three monitoring periods. The remote system produced a PR of 0.46. In both systems the PV arrays appear to have been oversized. This was due to overestimation of the energy requirements of the loads on the systems. In the laboratory system, the loads consisting of three compact fluorescent lamps and one incandescent lamp, were used to simulate a typical SHS load pro le and collectively consumed only 85 percent of their rated power. The 8 predicted load profile for the remote system proved to be signi cantly overestimated. The results of the monitoring project demonstrate the importance of acquiring an accurate estimation of the energy demand from loads on the system. Overestimations result in over-sized arrays and energy lost to charge control while under-sized systems risk damaging system batteries and load shedding. Significant under-performance of the PV module used in the laboratory system, underlines the importance of measuring module IV curves and verifying manufacturer specifications before system deployment. It was also found that signi cant PV array performance gains could be obtained by the use of maximum power point tracking charge controllers. Increased PV array performance leads to smaller arrays and reduced system cost.
- Full Text:
- Date Issued: 2011
- Authors: Williams, Nathaniel John
- Date: 2011
- Subjects: Photovoltaic cells , Dwellings -- Power supply
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10516 , http://hdl.handle.net/10948/1308 , Photovoltaic cells , Dwellings -- Power supply
- Description: It is estimated that 1.6 billion people today live without access to electricity. Most of these people live in remote rural areas in developing countries. One economic solution to this problem is the deployment of small domestic photovoltaic (PV) systems called solar home systems (SHS). In order to improve the performance and reduce the life cycle cost of these systems, accurate monitoring data of real SHSs is required. To this end, two SHSs typical of those found in the field were designed and installed, one in a rural area of the Eastern Cape of South Africa and the other in the laboratory. Monitoring systems were designed to record energy ows in the system and important environmental parameters. A novel technique was developed to correct for measurement errors occurring during the utilization of pulse width modulation charge control techniques. These errors were found to be as large as 47.6 percent. Simulations show that correction techniques produce measurement errors that are up to 20 times smaller than uncorrected values, depending upon the operating conditions. As a tool to aid in the analysis of monitoring data, a PV performance model was developed. The model, used to predict the maximum power point (MPP) power of a PV array, was able to predict MPP energy production to within 0.2 percent over the course of three days. Monitoring data from the laboratory system shows that the largest sources of energy loss are charge control, module under performance relative to manufacturer specifications and operation of the PV array away from MPP. These accounted for losses of approximately 18-27 percent, 15 percent and 8-11 percent of rated PV energy under standard test conditions, respectively. Energy consumed by loads on the systems was less than 50 percent of rated PV energy for both the remote and laboratory systems. Performance ratios (PR) for the laboratory system ranged from 0.38 to 0.49 for the three monitoring periods. The remote system produced a PR of 0.46. In both systems the PV arrays appear to have been oversized. This was due to overestimation of the energy requirements of the loads on the systems. In the laboratory system, the loads consisting of three compact fluorescent lamps and one incandescent lamp, were used to simulate a typical SHS load pro le and collectively consumed only 85 percent of their rated power. The 8 predicted load profile for the remote system proved to be signi cantly overestimated. The results of the monitoring project demonstrate the importance of acquiring an accurate estimation of the energy demand from loads on the system. Overestimations result in over-sized arrays and energy lost to charge control while under-sized systems risk damaging system batteries and load shedding. Significant under-performance of the PV module used in the laboratory system, underlines the importance of measuring module IV curves and verifying manufacturer specifications before system deployment. It was also found that signi cant PV array performance gains could be obtained by the use of maximum power point tracking charge controllers. Increased PV array performance leads to smaller arrays and reduced system cost.
- Full Text:
- Date Issued: 2011
A study of mathematics instructional practices in foundation phase grade three classrooms in East London
- Authors: Williams, Beverley Diana
- Date: 2011
- Subjects: Mathematics--Study and teaching (Primary) http://id.loc.gov/authorities/subjects/sh85082164 , Mathematics--Study and teaching (Elementary) http://id.loc.gov/authorities/subjects/sh85082163
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/19585 , vital:43146
- Description: This study describes the instructional practices of grade three teachers in their attempt to facilitate mathematical learning. The teachers’ practices are described in relation to the requirements of the revised National Curriculum Statement. In order to demarcate the field of investigation, the researcher provides an overview of the historical background of the study and draws attention to the knowledge interest of the investigation. The problem, the research questions, the assumptions of the study, the significance of the study, the rationale and the delimitation of the study are all set out in this chapter. A list of the major terms used in the study is also given. In concluding the chapter and outline of the issues discussed in each of the five chapters is given. , Thesis (MEd) -- University of Fort Hare, 2011
- Full Text:
- Date Issued: 2011
- Authors: Williams, Beverley Diana
- Date: 2011
- Subjects: Mathematics--Study and teaching (Primary) http://id.loc.gov/authorities/subjects/sh85082164 , Mathematics--Study and teaching (Elementary) http://id.loc.gov/authorities/subjects/sh85082163
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/19585 , vital:43146
- Description: This study describes the instructional practices of grade three teachers in their attempt to facilitate mathematical learning. The teachers’ practices are described in relation to the requirements of the revised National Curriculum Statement. In order to demarcate the field of investigation, the researcher provides an overview of the historical background of the study and draws attention to the knowledge interest of the investigation. The problem, the research questions, the assumptions of the study, the significance of the study, the rationale and the delimitation of the study are all set out in this chapter. A list of the major terms used in the study is also given. In concluding the chapter and outline of the issues discussed in each of the five chapters is given. , Thesis (MEd) -- University of Fort Hare, 2011
- Full Text:
- Date Issued: 2011
A comparative analysis of the intermediary systems in South Africa, Namibia, Zimbabwe and Ethiopia
- Authors: Wilkerson, Tendai Marowa
- Date: 2011
- Subjects: Juvenile courts -- South Africa , Juvenile courts -- Namibia , Juveline courts -- Zimbabwe , Juvenile courts -- Ethiopia , Children -- Legal status, laws, etc. -- South Africa , Children -- Legal status, laws, etc. -- Namibia , Children -- Legal status, laws, etc. -- Zimbabwe , Children -- Legal status, laws, etc. -- Ethiopia , Child witnesses -- South Africa , Child witnesses -- Namibia , Child witnesses -- Zimbabwe , Child witnesses -- Ethiopia , Mediation -- Law and legislation -- South Africa , Mediation -- Law and legislation -- Namibia , Mediation -- Law and legislation -- Zimbabwe , Mediation -- Law and legislation -- Ethiopia , Children's rights -- South Africa , Children's rights -- Namibia , Children's rights -- Zimbabwe , Children's rights -- Ethiopia
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:3698 , http://hdl.handle.net/10962/d1003213 , Juvenile courts -- South Africa , Juvenile courts -- Namibia , Juveline courts -- Zimbabwe , Juvenile courts -- Ethiopia , Children -- Legal status, laws, etc. -- South Africa , Children -- Legal status, laws, etc. -- Namibia , Children -- Legal status, laws, etc. -- Zimbabwe , Children -- Legal status, laws, etc. -- Ethiopia , Child witnesses -- South Africa , Child witnesses -- Namibia , Child witnesses -- Zimbabwe , Child witnesses -- Ethiopia , Mediation -- Law and legislation -- South Africa , Mediation -- Law and legislation -- Namibia , Mediation -- Law and legislation -- Zimbabwe , Mediation -- Law and legislation -- Ethiopia , Children's rights -- South Africa , Children's rights -- Namibia , Children's rights -- Zimbabwe , Children's rights -- Ethiopia
- Description: Prior to 1990, very few countries in the world offered special protection to child witnesses interfacing with the justice system. There were no legal provisions permitting testimonial accommodations for children in court. The courtroom experience was significantly traumatic for the children. With the international focus shifting from protecting and upholding the rights of the accused in the courtroom towards a more victim-centred approach, various international and regional instruments have strongly dvocated that children deserve special protection because of their vulnerability. In order for the courts to be able to elicit accurate evidence from the child without further traumatizing the child, research has shown that the child needs assistance. An intermediary may be defined as a person who facilitates communication between the child and the courtroom in a manner that takes into account the child‟s cognitive and developmental limitations. The thesis was prompted by the need to make a contribution to the currently limited body of literature on the intermediary systems in South Africa, Namibia, Zimbabwe and Ethiopia by investigating how the systems can be improved and sustained in a way that helps to protect the child witness in court. Despite the problems the South African courts have had in identifying the appropriate interpretation of its intermediary legislation, the country emerges as a clear leader for the steps it took by creating a positive legal framework within which child protection issues are addressed and introducing the concept of the intermediary. This concept proved to be an inspiration to its neighbours, Namibia and Zimbabwe. The influence of the South African intermediary legislation is evident in the Namibian and Zimbabwean legislation. Although Namibian legislators have drafted laws that permit intermediary assistance in court, there are as yet no intermediaries appointed. In Ethiopia, although there is no discernible intermediary legislation, the country has managed to establish an intermediary system. As a result of the analysis conducted, it is evident that the efficacy of the intermediary system is dependent on the presence of an enabling legislation, its clarity and ease of interpretation, the sensitisation of court role players on child vulnerabilities, the significance of intermediary assistance, and finally a government's commitment towards the implementation process.
- Full Text:
- Date Issued: 2011
- Authors: Wilkerson, Tendai Marowa
- Date: 2011
- Subjects: Juvenile courts -- South Africa , Juvenile courts -- Namibia , Juveline courts -- Zimbabwe , Juvenile courts -- Ethiopia , Children -- Legal status, laws, etc. -- South Africa , Children -- Legal status, laws, etc. -- Namibia , Children -- Legal status, laws, etc. -- Zimbabwe , Children -- Legal status, laws, etc. -- Ethiopia , Child witnesses -- South Africa , Child witnesses -- Namibia , Child witnesses -- Zimbabwe , Child witnesses -- Ethiopia , Mediation -- Law and legislation -- South Africa , Mediation -- Law and legislation -- Namibia , Mediation -- Law and legislation -- Zimbabwe , Mediation -- Law and legislation -- Ethiopia , Children's rights -- South Africa , Children's rights -- Namibia , Children's rights -- Zimbabwe , Children's rights -- Ethiopia
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:3698 , http://hdl.handle.net/10962/d1003213 , Juvenile courts -- South Africa , Juvenile courts -- Namibia , Juveline courts -- Zimbabwe , Juvenile courts -- Ethiopia , Children -- Legal status, laws, etc. -- South Africa , Children -- Legal status, laws, etc. -- Namibia , Children -- Legal status, laws, etc. -- Zimbabwe , Children -- Legal status, laws, etc. -- Ethiopia , Child witnesses -- South Africa , Child witnesses -- Namibia , Child witnesses -- Zimbabwe , Child witnesses -- Ethiopia , Mediation -- Law and legislation -- South Africa , Mediation -- Law and legislation -- Namibia , Mediation -- Law and legislation -- Zimbabwe , Mediation -- Law and legislation -- Ethiopia , Children's rights -- South Africa , Children's rights -- Namibia , Children's rights -- Zimbabwe , Children's rights -- Ethiopia
- Description: Prior to 1990, very few countries in the world offered special protection to child witnesses interfacing with the justice system. There were no legal provisions permitting testimonial accommodations for children in court. The courtroom experience was significantly traumatic for the children. With the international focus shifting from protecting and upholding the rights of the accused in the courtroom towards a more victim-centred approach, various international and regional instruments have strongly dvocated that children deserve special protection because of their vulnerability. In order for the courts to be able to elicit accurate evidence from the child without further traumatizing the child, research has shown that the child needs assistance. An intermediary may be defined as a person who facilitates communication between the child and the courtroom in a manner that takes into account the child‟s cognitive and developmental limitations. The thesis was prompted by the need to make a contribution to the currently limited body of literature on the intermediary systems in South Africa, Namibia, Zimbabwe and Ethiopia by investigating how the systems can be improved and sustained in a way that helps to protect the child witness in court. Despite the problems the South African courts have had in identifying the appropriate interpretation of its intermediary legislation, the country emerges as a clear leader for the steps it took by creating a positive legal framework within which child protection issues are addressed and introducing the concept of the intermediary. This concept proved to be an inspiration to its neighbours, Namibia and Zimbabwe. The influence of the South African intermediary legislation is evident in the Namibian and Zimbabwean legislation. Although Namibian legislators have drafted laws that permit intermediary assistance in court, there are as yet no intermediaries appointed. In Ethiopia, although there is no discernible intermediary legislation, the country has managed to establish an intermediary system. As a result of the analysis conducted, it is evident that the efficacy of the intermediary system is dependent on the presence of an enabling legislation, its clarity and ease of interpretation, the sensitisation of court role players on child vulnerabilities, the significance of intermediary assistance, and finally a government's commitment towards the implementation process.
- Full Text:
- Date Issued: 2011
Using social marketing to bridge the gap between systematic conservation planning and implementation at the local government level
- Authors: Wilhelm-Rechmann, Angelika
- Date: 2011
- Subjects: Nature conservation -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10603 , http://hdl.handle.net/10948/1550 , Nature conservation -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape
- Description: The study presented here describes an attempt to bridge the gap between systematic conservation assessment and decision-making for land-use planning in the Eastern Cape province, South Africa. The aim was to investigate how to effectively convince officials concerned with land use planning processes in the local municipal sphere to include conservation priorities meaningfully in their processes. The approach used to reach this aim was social marketing, the use of marketing technologies and concepts to effect behavior changes to further societal good. So far social marketing is not commonly used in the conservation domain; I therefore aimed also at proving the usefulness of this approach for conservation. Following the introduction which provides background to the project and a more detailed summary, Chapter 2 provides a detailed and comprehensive review of the considerations and concepts regarding the use of social marketing in a context geared at protecting nature. The research on the primary target group for this study, officials concerned with land use planning processes in the local municipal sphere is described in Chapter 3. The main outcomes were that land use planners perceive few needs with regards to implementing the incorporation of biodiversity conservation issues in the land use planning process, and that the deficiencies in the land use planning process per se, as well as the lack of recognition in the political sphere (the domain of elected councilors), represent the core barriers to adopting the conservation priorities. I conclude that to effect behavior change towards adoption of conservation priorities the land use planning processes need to be supported and the political sphere need to be included in the behavior change process. 6 Chapter 4 therefore focuses on the new target group that emerged as essential in the previous chapter, locally elected councilors. I found that councilors do actually consider land use planning procedures as being important, but also as being dysfunctional. Councilors do value their natural environment for themselves as well as for its tourism value, but most councilors had little understanding of what the term “biodiversity” means and did not connect the term “sustainability” with the natural environment. It became also evident, that councilors do not see conservation in a predominantly positive manner. Chapter 5 therefore yields insight on councilor’s perception that environmental protection and development are mutually exclusive, and the negative frames attached to the conservation endeavor as being socially unjust, disrespectful and utopian. In Chapter 6 I investigated the usefulness of a tractable and well established measure of environmental attitudes or beliefs. I assessed my target audience’s responses to the New Ecological Paradigm scale and the Inclusion of Nature in Self scale. I conclude in Chapter 7 with an account of the difficulties I encountered during the project, an assessment of my project from a social marketing perspective, components of my project that did not yield the results expected, and a proposal for future research.
- Full Text:
- Date Issued: 2011
- Authors: Wilhelm-Rechmann, Angelika
- Date: 2011
- Subjects: Nature conservation -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10603 , http://hdl.handle.net/10948/1550 , Nature conservation -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape
- Description: The study presented here describes an attempt to bridge the gap between systematic conservation assessment and decision-making for land-use planning in the Eastern Cape province, South Africa. The aim was to investigate how to effectively convince officials concerned with land use planning processes in the local municipal sphere to include conservation priorities meaningfully in their processes. The approach used to reach this aim was social marketing, the use of marketing technologies and concepts to effect behavior changes to further societal good. So far social marketing is not commonly used in the conservation domain; I therefore aimed also at proving the usefulness of this approach for conservation. Following the introduction which provides background to the project and a more detailed summary, Chapter 2 provides a detailed and comprehensive review of the considerations and concepts regarding the use of social marketing in a context geared at protecting nature. The research on the primary target group for this study, officials concerned with land use planning processes in the local municipal sphere is described in Chapter 3. The main outcomes were that land use planners perceive few needs with regards to implementing the incorporation of biodiversity conservation issues in the land use planning process, and that the deficiencies in the land use planning process per se, as well as the lack of recognition in the political sphere (the domain of elected councilors), represent the core barriers to adopting the conservation priorities. I conclude that to effect behavior change towards adoption of conservation priorities the land use planning processes need to be supported and the political sphere need to be included in the behavior change process. 6 Chapter 4 therefore focuses on the new target group that emerged as essential in the previous chapter, locally elected councilors. I found that councilors do actually consider land use planning procedures as being important, but also as being dysfunctional. Councilors do value their natural environment for themselves as well as for its tourism value, but most councilors had little understanding of what the term “biodiversity” means and did not connect the term “sustainability” with the natural environment. It became also evident, that councilors do not see conservation in a predominantly positive manner. Chapter 5 therefore yields insight on councilor’s perception that environmental protection and development are mutually exclusive, and the negative frames attached to the conservation endeavor as being socially unjust, disrespectful and utopian. In Chapter 6 I investigated the usefulness of a tractable and well established measure of environmental attitudes or beliefs. I assessed my target audience’s responses to the New Ecological Paradigm scale and the Inclusion of Nature in Self scale. I conclude in Chapter 7 with an account of the difficulties I encountered during the project, an assessment of my project from a social marketing perspective, components of my project that did not yield the results expected, and a proposal for future research.
- Full Text:
- Date Issued: 2011
Nelson Mandela Metropolitan University students' perceptions of sexualised advertisements of three South African fast food brands
- Authors: Wignall, Andrea
- Date: 2011
- Subjects: Sex in advertising -- South Africa -- Childhood and youth , Food industry and trade -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:8408 , http://hdl.handle.net/10948/d1011443 , Sex in advertising -- South Africa -- Childhood and youth , Food industry and trade -- South Africa
- Description: This research study aimed to provide the South African fast food industry and their advertising representatives with insights into 18-28-year-olds‟ perception of using sexual appeal to elicit their attention, and whether using this advertising technique is gaining positive brand recognition with this target market. This research study aimed to determine the selected sample‟s (NMMU students) perceptions of three South African fast food brands, namely KFC, Nando’s and Steers, in terms of their use of sexualised fast food advertisements. An electronic survey questionnaire was conducted with both closed and open-ended questions relating to the use of sexual appeal in advertising within the three South African fast food brands. The survey questionnaire helped determine what the selected sample‟s perceptions were of each advertisement, and whether the use of sexual appeal captured their attention. A semiotic analysis of each advertisement was conducted to determine if the advertisements do contain the use of sexual appeal, by examining the sign. This includes looking at the three aspects of a sign namely the signifier, the referent and the signified. In terms of this study, the signifier represents the T.V. advertisements; the signified represents the meaning of the advertisements and the referent represents to what the advertisements are initially referring. The results of the study indicated that each of the three fast food advertisements incorporated the use of sexual appeal in varying degrees. Respondents indicated that the sexual appeal in the advertisements was appropriate if they were directed at the right age group. The respondents indicated that these three advertisements were more likely to attract the males, in the target market and they felt that the advertisements leaned towards objectifying the women, which would be offensive to the females in the target market. It was determined that if the advertisements contained humour, they were more effective and memorable.
- Full Text:
- Date Issued: 2011
- Authors: Wignall, Andrea
- Date: 2011
- Subjects: Sex in advertising -- South Africa -- Childhood and youth , Food industry and trade -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:8408 , http://hdl.handle.net/10948/d1011443 , Sex in advertising -- South Africa -- Childhood and youth , Food industry and trade -- South Africa
- Description: This research study aimed to provide the South African fast food industry and their advertising representatives with insights into 18-28-year-olds‟ perception of using sexual appeal to elicit their attention, and whether using this advertising technique is gaining positive brand recognition with this target market. This research study aimed to determine the selected sample‟s (NMMU students) perceptions of three South African fast food brands, namely KFC, Nando’s and Steers, in terms of their use of sexualised fast food advertisements. An electronic survey questionnaire was conducted with both closed and open-ended questions relating to the use of sexual appeal in advertising within the three South African fast food brands. The survey questionnaire helped determine what the selected sample‟s perceptions were of each advertisement, and whether the use of sexual appeal captured their attention. A semiotic analysis of each advertisement was conducted to determine if the advertisements do contain the use of sexual appeal, by examining the sign. This includes looking at the three aspects of a sign namely the signifier, the referent and the signified. In terms of this study, the signifier represents the T.V. advertisements; the signified represents the meaning of the advertisements and the referent represents to what the advertisements are initially referring. The results of the study indicated that each of the three fast food advertisements incorporated the use of sexual appeal in varying degrees. Respondents indicated that the sexual appeal in the advertisements was appropriate if they were directed at the right age group. The respondents indicated that these three advertisements were more likely to attract the males, in the target market and they felt that the advertisements leaned towards objectifying the women, which would be offensive to the females in the target market. It was determined that if the advertisements contained humour, they were more effective and memorable.
- Full Text:
- Date Issued: 2011
Empowering teachers to render learner support to learners who experience reading barriers
- Authors: Wienand, Merna Adeliade
- Date: 2011
- Subjects: Inclusive eduction
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:9497 , http://hdl.handle.net/10948/1353 , Inclusive eduction
- Description: In this qualitative study the researcher provided proposed guidelines to empower teachers to render learner support to learners who experience reading barriers. A literature study was undertaken to investigate the importance and consequences of inclusive education, the need for a systematic approach, reading problems and its causes and remediation thereof. The empirical study includes interviews with important stakeholders and observations. The results of the empirical study culminated into proposed guidelines to empower teachers to render learner support to these learners. Recommendations were made based on the literature study and the results of the empirical research
- Full Text:
- Date Issued: 2011
- Authors: Wienand, Merna Adeliade
- Date: 2011
- Subjects: Inclusive eduction
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:9497 , http://hdl.handle.net/10948/1353 , Inclusive eduction
- Description: In this qualitative study the researcher provided proposed guidelines to empower teachers to render learner support to learners who experience reading barriers. A literature study was undertaken to investigate the importance and consequences of inclusive education, the need for a systematic approach, reading problems and its causes and remediation thereof. The empirical study includes interviews with important stakeholders and observations. The results of the empirical study culminated into proposed guidelines to empower teachers to render learner support to these learners. Recommendations were made based on the literature study and the results of the empirical research
- Full Text:
- Date Issued: 2011
Aardvark burrows: a potential resource for animals in arid and semi-arid environments
- Whittington-Jones, Gareth M, Bernard, Ric T F, Parker, Daniel M
- Authors: Whittington-Jones, Gareth M , Bernard, Ric T F , Parker, Daniel M
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443852 , vital:74166 , https://doi.org/10.1080/15627020.2011.11407509
- Description: Arid and semi-arid environments are characterized by extreme fluctuations in temperature and low rainfall, which present significant challenges to the animals inhabiting these areas. However, the presence of burrows may allow animals to avoid climatic extremes and predators and may act as valuable foraging sites. We assessed the microhabitat conditions (maximum and minimum temperature, relative humidity and seed abundance) of aardvark (Orycteropus afer) burrows in relation to paired non-burrow areas at three sites in South Africa. We also describe the extent to which they are used as resources by other vertebrates. Maximum temperatures were significantly lower and minimum temperatures and relative humidity values were significantly higher inside the burrows than outside. The concentration of seeds inside the burrows and at the paired non-burrow sites was similar. Twenty-seven vertebrate species (21 mammals, two birds, three reptiles and one amphibian) were recorded making use of the burrows and it is likely that these species accrue benefits (e.g. a buffered microclimate) from burrow use. However, our sampling was biased towards mammals and nocturnal species. Consequently, we recommend further work to establish the overall reliance of vertebrate taxa on aardvark burrows in arid and semi-arid environments.
- Full Text:
- Date Issued: 2011
- Authors: Whittington-Jones, Gareth M , Bernard, Ric T F , Parker, Daniel M
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443852 , vital:74166 , https://doi.org/10.1080/15627020.2011.11407509
- Description: Arid and semi-arid environments are characterized by extreme fluctuations in temperature and low rainfall, which present significant challenges to the animals inhabiting these areas. However, the presence of burrows may allow animals to avoid climatic extremes and predators and may act as valuable foraging sites. We assessed the microhabitat conditions (maximum and minimum temperature, relative humidity and seed abundance) of aardvark (Orycteropus afer) burrows in relation to paired non-burrow areas at three sites in South Africa. We also describe the extent to which they are used as resources by other vertebrates. Maximum temperatures were significantly lower and minimum temperatures and relative humidity values were significantly higher inside the burrows than outside. The concentration of seeds inside the burrows and at the paired non-burrow sites was similar. Twenty-seven vertebrate species (21 mammals, two birds, three reptiles and one amphibian) were recorded making use of the burrows and it is likely that these species accrue benefits (e.g. a buffered microclimate) from burrow use. However, our sampling was biased towards mammals and nocturnal species. Consequently, we recommend further work to establish the overall reliance of vertebrate taxa on aardvark burrows in arid and semi-arid environments.
- Full Text:
- Date Issued: 2011
The entrepreneurial orientation of selected ICT SMME's
- Authors: Whittaker, Donna
- Date: 2011
- Subjects: Business enterprises , Information technology
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:8754 , http://hdl.handle.net/10948/d1011417 , Business enterprises , Information technology
- Description: Despite the demand for ICT skills, businesses are experiencing an ICT skills shortage. Constantly changing ICT technologies require business leaders to find qualified ICT professionals to implement new business strategies and business processes. The Information and Communications Technology (ICT) sector is experiencing a continued skills shortage and various initiatives have been launched to address the problem. Businesses continually struggle to find qualified and suitably skilled ICT personnel. As a result businesses have had to outsource their ICT requirements off-shore to obtain the required ICT skills and maintain their competitive advantage. In a country desperate for job creation, entrepreneurial inclination and start up of new businesses may play a pivotal role in the economic development and well being of individuals able to capitalise on the availability of ICT opportunities. Entrepreneurship is a critical factor in promoting innovation, creating employment opportunities and generating social and economic wealth in a country's economy. Sectors such as Information and Communication Technologies can be seen as archetypal entrepreneurial industries and can consequently play a key role in economic development. In the research that follows the author identifies an ICT skills shortage in South Africa. This is followed by an exploratory study that investigates the influence of psychological traits and socio-cultural variables on the entrepreneurial intent of selected ICT SMME’s in the Nelson Mandela Metropolitan Area. The findings revealed that both psychological traits together with socio-cultural variables influence an individual’s intention to start up a business. The predominant psychological trait discovered during the research was perseverance. Family environmental issues were the dominant socio-cultural variable influencing entrepreneurial intention amongst the case study subjects.
- Full Text:
- Date Issued: 2011
- Authors: Whittaker, Donna
- Date: 2011
- Subjects: Business enterprises , Information technology
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:8754 , http://hdl.handle.net/10948/d1011417 , Business enterprises , Information technology
- Description: Despite the demand for ICT skills, businesses are experiencing an ICT skills shortage. Constantly changing ICT technologies require business leaders to find qualified ICT professionals to implement new business strategies and business processes. The Information and Communications Technology (ICT) sector is experiencing a continued skills shortage and various initiatives have been launched to address the problem. Businesses continually struggle to find qualified and suitably skilled ICT personnel. As a result businesses have had to outsource their ICT requirements off-shore to obtain the required ICT skills and maintain their competitive advantage. In a country desperate for job creation, entrepreneurial inclination and start up of new businesses may play a pivotal role in the economic development and well being of individuals able to capitalise on the availability of ICT opportunities. Entrepreneurship is a critical factor in promoting innovation, creating employment opportunities and generating social and economic wealth in a country's economy. Sectors such as Information and Communication Technologies can be seen as archetypal entrepreneurial industries and can consequently play a key role in economic development. In the research that follows the author identifies an ICT skills shortage in South Africa. This is followed by an exploratory study that investigates the influence of psychological traits and socio-cultural variables on the entrepreneurial intent of selected ICT SMME’s in the Nelson Mandela Metropolitan Area. The findings revealed that both psychological traits together with socio-cultural variables influence an individual’s intention to start up a business. The predominant psychological trait discovered during the research was perseverance. Family environmental issues were the dominant socio-cultural variable influencing entrepreneurial intention amongst the case study subjects.
- Full Text:
- Date Issued: 2011
Thermal degradation of diamond compacts: a TEM investigation
- Authors: Westraadt, Johan Ewald
- Date: 2011
- Subjects: Materials -- Thermal properties Chemical weathering
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/10829 , vital:26827
- Description: Diamond compacts consist of fine diamond grains bonded together by using high pressure and high temperature. In this study transmission electron microscopy (TEM)was used to study thermal degradation of diamond compacts. Three different types of diamond compacts – namely cobalt polycrystalline diamond (PCD), calcium carbonate PCD, and diamond-SiC composites – were investigated with TEM to understand the processes that occur during synthesis. These compacts were then heated in inert atmospheres and the chemical changes studied with TEM. It was found that PCD, using cobalt as a bonding agent, will degrade after exposure to temperatures above 750ºC. The cobalt pools contain tungsten in solid solution. During heat treatment above 700ºC the solid solution tungsten combines with cobalt and dissolved carbon to form η-phase particles at the cobalt/diamond interface. At higher temperatures or insufficient tungsten levels the rate of dissolved carbon, into the cobalt pool, is too high and the excess carbon will form as graphite in the cobalt pool. Increased levels of solid solution tungsten, in the cobalt, is expected to delay the onset of graphitization in the diamond compact, thereby increasing the thermal stability of the diamond compact. Non-metallic PCD using calcium carbonate as a bonding agent was successfully sintered in this study. TEM revealed similar micro-structural features as in cobalt based PCD. No signs of thermal degradation were found after exposure to 1200ºC in vacuum for this PCD. Contaminants introduced during processing prevented a detailed study of the binder in this system. The effect of substitutional metal atoms and plastic deformation of diamond on the thermal stability of diamond-SiC composites were investigated. A piston cylinder press was developed and used to synthesize diamond-SiC composites with different levels of plastically deformed diamond. It was concluded that substitutional metal atoms and plastic deformation of diamond grains play no role in the thermal degradation of diamond compacts at 750ºC. The thermal degradation of cobalt PCD is therefore completely determined by the cobalt/diamond interaction at 750ºC.
- Full Text:
- Date Issued: 2011
- Authors: Westraadt, Johan Ewald
- Date: 2011
- Subjects: Materials -- Thermal properties Chemical weathering
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/10829 , vital:26827
- Description: Diamond compacts consist of fine diamond grains bonded together by using high pressure and high temperature. In this study transmission electron microscopy (TEM)was used to study thermal degradation of diamond compacts. Three different types of diamond compacts – namely cobalt polycrystalline diamond (PCD), calcium carbonate PCD, and diamond-SiC composites – were investigated with TEM to understand the processes that occur during synthesis. These compacts were then heated in inert atmospheres and the chemical changes studied with TEM. It was found that PCD, using cobalt as a bonding agent, will degrade after exposure to temperatures above 750ºC. The cobalt pools contain tungsten in solid solution. During heat treatment above 700ºC the solid solution tungsten combines with cobalt and dissolved carbon to form η-phase particles at the cobalt/diamond interface. At higher temperatures or insufficient tungsten levels the rate of dissolved carbon, into the cobalt pool, is too high and the excess carbon will form as graphite in the cobalt pool. Increased levels of solid solution tungsten, in the cobalt, is expected to delay the onset of graphitization in the diamond compact, thereby increasing the thermal stability of the diamond compact. Non-metallic PCD using calcium carbonate as a bonding agent was successfully sintered in this study. TEM revealed similar micro-structural features as in cobalt based PCD. No signs of thermal degradation were found after exposure to 1200ºC in vacuum for this PCD. Contaminants introduced during processing prevented a detailed study of the binder in this system. The effect of substitutional metal atoms and plastic deformation of diamond on the thermal stability of diamond-SiC composites were investigated. A piston cylinder press was developed and used to synthesize diamond-SiC composites with different levels of plastically deformed diamond. It was concluded that substitutional metal atoms and plastic deformation of diamond grains play no role in the thermal degradation of diamond compacts at 750ºC. The thermal degradation of cobalt PCD is therefore completely determined by the cobalt/diamond interaction at 750ºC.
- Full Text:
- Date Issued: 2011
Vocabulary development in a grade 7 class using dictionary skills: an action research project
- Authors: Wells, Stephanie Alice
- Date: 2011
- Subjects: English language -- Study and teaching (Elementary) -- South Africa -- Eastern Cape Vocabulary -- Study and teaching (Elementary) -- South Africa -- Eastern Cape English language Dictionaries -- Polyglot -- Study and teaching (Elementary) -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1822 , http://hdl.handle.net/10962/d1003708
- Description: As I was involved as a voluntary, part-time teacher in a local, semi-rural school in the Eastern Cape, South Africa, I became increasingly aware of the learners' lack of English literacy. I therefore decided to do a practical research on vocabulary development, focusing on dictionary skills. In this thesis I describe how I implemented a vocabulary development programme as an Action Research project. My research group was a grade 7 class of English First Additional Language learners who had minimal exposure to English at school and in their communities. The class was a mixture of Afrikaans and isiXhosa home language speakers and the medium of instruction was Afrikaans. The school served a low-income community and was poorly resourced. As dictionary skills is a requirement of the national curriculum, I used 10 time-tabled lessons over a 5 week period to introduce the learners to dictionaries. My data sources were a journal detailing my reflections on each lesson; a video-recording of the lessons; small group interviews after each lesson which were audio-recorded; tasksheets on the work covered in class and questionnaires asking the learners for written responses to the lessons. The class teacher who filmed the lessons was also asked for feedback during and after the programme. My goals were to assess my teaching approach in these circumstances and to what extent the outcomes were positive for the learners. As I had come from a background of English Home Language teaching in good, well-resourced schools I found I had to question many of my assumptions. Although I was an experienced, qualified and confident teacher, I was continually having to reassess my teaching methods which were being challenged by very different classroom conditions. The outcomes of the research show why I was not able to achieve what I had thought I could in the time given.
- Full Text:
- Date Issued: 2011
- Authors: Wells, Stephanie Alice
- Date: 2011
- Subjects: English language -- Study and teaching (Elementary) -- South Africa -- Eastern Cape Vocabulary -- Study and teaching (Elementary) -- South Africa -- Eastern Cape English language Dictionaries -- Polyglot -- Study and teaching (Elementary) -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1822 , http://hdl.handle.net/10962/d1003708
- Description: As I was involved as a voluntary, part-time teacher in a local, semi-rural school in the Eastern Cape, South Africa, I became increasingly aware of the learners' lack of English literacy. I therefore decided to do a practical research on vocabulary development, focusing on dictionary skills. In this thesis I describe how I implemented a vocabulary development programme as an Action Research project. My research group was a grade 7 class of English First Additional Language learners who had minimal exposure to English at school and in their communities. The class was a mixture of Afrikaans and isiXhosa home language speakers and the medium of instruction was Afrikaans. The school served a low-income community and was poorly resourced. As dictionary skills is a requirement of the national curriculum, I used 10 time-tabled lessons over a 5 week period to introduce the learners to dictionaries. My data sources were a journal detailing my reflections on each lesson; a video-recording of the lessons; small group interviews after each lesson which were audio-recorded; tasksheets on the work covered in class and questionnaires asking the learners for written responses to the lessons. The class teacher who filmed the lessons was also asked for feedback during and after the programme. My goals were to assess my teaching approach in these circumstances and to what extent the outcomes were positive for the learners. As I had come from a background of English Home Language teaching in good, well-resourced schools I found I had to question many of my assumptions. Although I was an experienced, qualified and confident teacher, I was continually having to reassess my teaching methods which were being challenged by very different classroom conditions. The outcomes of the research show why I was not able to achieve what I had thought I could in the time given.
- Full Text:
- Date Issued: 2011
Bayesian logistic regression models for credit scoring
- Authors: Webster, Gregg
- Date: 2011
- Subjects: Bayesian statistical decision theory Credit scoring systems Regression analysis Logistic regression analysis Monte Carlo method Markov processes Financial institutions
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:5574 , http://hdl.handle.net/10962/d1005538
- Description: The Bayesian approach to logistic regression modelling for credit scoring is useful when there are data quantity issues. Data quantity issues might occur when a bank is opening in a new location or there is change in the scoring procedure. Making use of prior information (available from the coefficients estimated on other data sets, or expert knowledge about the coefficients) a Bayesian approach is proposed to improve the credit scoring models. To achieve this, a data set is split into two sets, “old” data and “new” data. Priors are obtained from a model fitted on the “old” data. This model is assumed to be a scoring model used by a financial institution in the current location. The financial institution is then assumed to expand into a new economic location where there is limited data. The priors from the model on the “old” data are then combined in a Bayesian model with the “new” data to obtain a model which represents all the available information. The predictive performance of this Bayesian model is compared to a model which does not make use of any prior information. It is found that the use of relevant prior information improves the predictive performance when the size of the “new” data is small. As the size of the “new” data increases, the importance of including prior information decreases
- Full Text:
- Date Issued: 2011
- Authors: Webster, Gregg
- Date: 2011
- Subjects: Bayesian statistical decision theory Credit scoring systems Regression analysis Logistic regression analysis Monte Carlo method Markov processes Financial institutions
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:5574 , http://hdl.handle.net/10962/d1005538
- Description: The Bayesian approach to logistic regression modelling for credit scoring is useful when there are data quantity issues. Data quantity issues might occur when a bank is opening in a new location or there is change in the scoring procedure. Making use of prior information (available from the coefficients estimated on other data sets, or expert knowledge about the coefficients) a Bayesian approach is proposed to improve the credit scoring models. To achieve this, a data set is split into two sets, “old” data and “new” data. Priors are obtained from a model fitted on the “old” data. This model is assumed to be a scoring model used by a financial institution in the current location. The financial institution is then assumed to expand into a new economic location where there is limited data. The priors from the model on the “old” data are then combined in a Bayesian model with the “new” data to obtain a model which represents all the available information. The predictive performance of this Bayesian model is compared to a model which does not make use of any prior information. It is found that the use of relevant prior information improves the predictive performance when the size of the “new” data is small. As the size of the “new” data increases, the importance of including prior information decreases
- Full Text:
- Date Issued: 2011
An investigation into knowledge and change in a Grade 9 environmental research project
- Authors: Webber, Susan Marion
- Date: 2011
- Subjects: Environmental education -- Activity programs -- South Africa Environmental education -- Evaluation -- South Africa Environmental education -- Study and teaching (Secondary) -- South Africa Sustainable development -- Evaluation -- South Africa Sustainable development -- Study and teaching (Secondary) -- South Africa Active learning -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1597 , http://hdl.handle.net/10962/d1003479
- Description: This study considers a Grade 9 Integrated Environmental Research Project which was implemented as a vehicle to induce knowledge-based change in learners. It was noted that change did not occur as hoped, and this study was undertaken to review the Grade 9 Project in order to improve it and to probe the apparent gap between knowledge and action. The study generated evidence on the learning processes within the project. This revealed a number of contradictions and tensions which limit change initiatives within the local environment. Notable here was a contradictory mandate between undertaking a research-based change project and responding to the rubric of assessment which was not linked to the research done. It was found that faced with this dual mandate, learners chose to focus on the assessment-laden mandate as this was the ultimate agenda that would reap the reward within the traditional school environment. The study examines the gap between knowledge and practice to probe ways in which to close this gap in the context of an environmental research assignment. The outcome is a recommendation that we as the project designers review the evidence of tensions and contradictions revealed in the study to reflect on the underlying purpose of the project and reshape it in light of recent literature on the challenges of social learning and change.
- Full Text:
- Date Issued: 2011
- Authors: Webber, Susan Marion
- Date: 2011
- Subjects: Environmental education -- Activity programs -- South Africa Environmental education -- Evaluation -- South Africa Environmental education -- Study and teaching (Secondary) -- South Africa Sustainable development -- Evaluation -- South Africa Sustainable development -- Study and teaching (Secondary) -- South Africa Active learning -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1597 , http://hdl.handle.net/10962/d1003479
- Description: This study considers a Grade 9 Integrated Environmental Research Project which was implemented as a vehicle to induce knowledge-based change in learners. It was noted that change did not occur as hoped, and this study was undertaken to review the Grade 9 Project in order to improve it and to probe the apparent gap between knowledge and action. The study generated evidence on the learning processes within the project. This revealed a number of contradictions and tensions which limit change initiatives within the local environment. Notable here was a contradictory mandate between undertaking a research-based change project and responding to the rubric of assessment which was not linked to the research done. It was found that faced with this dual mandate, learners chose to focus on the assessment-laden mandate as this was the ultimate agenda that would reap the reward within the traditional school environment. The study examines the gap between knowledge and practice to probe ways in which to close this gap in the context of an environmental research assignment. The outcome is a recommendation that we as the project designers review the evidence of tensions and contradictions revealed in the study to reflect on the underlying purpose of the project and reshape it in light of recent literature on the challenges of social learning and change.
- Full Text:
- Date Issued: 2011
The impact on the family dynamic of having a child and sibling with Down syndrome
- Authors: Webber, Heidi
- Date: 2011
- Subjects: Down syndrome , Children with disabilities -- Family relationships
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:9495 , http://hdl.handle.net/10948/1441 , Down syndrome , Children with disabilities -- Family relationships
- Description: The raison d'être of my research is simple: it’s about tossing one more starfish back into the surf. Down syndrome is not a disease, nor is it contagious or a death sentence (it only feels that way when you find out for the first time). At the moment of conception, the apprearance of extra genetic material results in a total of 47 chromosomes in every cell. Usually each cell has only 46, thus making an individual with Down syndrome far more like others than different from them. Yet, this extra chromosome presents special circumstances regarding their ability to acquire new skills, be it academic or practical, encompassing a specific learning profile with typical characterisitcs, strengths and weaknesses. Twenty-first century family life is simultaneously challenging and richly rewarding and the expectancy of most families are of a life lived on paved highways with well-marked signs, and rest stops never far apart. Adding an extra chromosome to the luggage sends the family travelling down a vastly different highway instead, not always knowing what is ahead. It’s scary, but in reality even those on the wide smooth roads do not know the future. Echoing the feelings of many parents, Leonard (1992: 5) states, “The trouble is that we have few, if any maps to guide us on the journey or show us how to find the path…” Assumptions from previous decades that used to increase stress associated with rearing a child with Down syndrome would negatively impact on individual family members and the family unit as such. This has made way for the growing consensus that it is not necessarily the norm. Whilst some families have trouble in adapting to the increased stress, other families adjust easier and even thrive. Successful adaptation seems more likely in resilient families who enjoy high levels of parental well-being and strong relationship bonds. Findings of this qualitative research study confirm that unresolved marital strains are more likely to result in divorce as opposed to the birth of their child with Down syndrome. Correspondingly, siblings of children with Down syndrome reported mostly positive impact than negated opportunities to participate in a normal childhood. My motivation for this research was to explore the nature of challenges faced by modern families and to provide mechanisms to facilitate positive adaptation for the family and aid vii inclusion of the child with Down syndrome into school and greater society. Recommendations are also presented for the medical professionals who, ironically, have proved to be the last people parents want to go for support, owing mostly to their decidedly objectionable treatment of parents; as well as the generally uninformed public, who seldom understand or support attempts of parents to include and expose their child to everyday experiences. In conclusion, I summarize: Should it be that I may influence but one person to see persons with Down syndrome for the potential that they hold instead of the associated problems of their condition, this would afford me the satisfaction and contentment knowing that I have succeeded in making a positive contribution to their plight. I would have successfully portrayed the families for the ordinary people they are with anticipations, aspirations and anxieties, but later tasting the elation of being empowered, and the resultant enjoyment and pride of the achievements of their extraordinary “starfish” child. The simple story below explains it all. A little boy was walking on the beach when he noticed scores of starfish washed onto the beach by the previous night’s high tide. He curiously watched as an old man bent down, came up slowly and tossed one starfish after the other into the surf. He went closer to investigate. “Excuse me, sir, what are you doing?” he enquired. The old man said: “I am throwing the starfish back into the ocean before they die, my boy…come, lend a hand”. The boy looked up and down the beach at the hundreds of starfish scattered along the shoreline. “But there’s too many…” said the boy, “it’ll make no difference!” The old man smiled, bent down, picked up another starfish, and carefully tossing it into the clear blue water, he replied, “…It makes a difference to this one…”
- Full Text:
- Date Issued: 2011
- Authors: Webber, Heidi
- Date: 2011
- Subjects: Down syndrome , Children with disabilities -- Family relationships
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:9495 , http://hdl.handle.net/10948/1441 , Down syndrome , Children with disabilities -- Family relationships
- Description: The raison d'être of my research is simple: it’s about tossing one more starfish back into the surf. Down syndrome is not a disease, nor is it contagious or a death sentence (it only feels that way when you find out for the first time). At the moment of conception, the apprearance of extra genetic material results in a total of 47 chromosomes in every cell. Usually each cell has only 46, thus making an individual with Down syndrome far more like others than different from them. Yet, this extra chromosome presents special circumstances regarding their ability to acquire new skills, be it academic or practical, encompassing a specific learning profile with typical characterisitcs, strengths and weaknesses. Twenty-first century family life is simultaneously challenging and richly rewarding and the expectancy of most families are of a life lived on paved highways with well-marked signs, and rest stops never far apart. Adding an extra chromosome to the luggage sends the family travelling down a vastly different highway instead, not always knowing what is ahead. It’s scary, but in reality even those on the wide smooth roads do not know the future. Echoing the feelings of many parents, Leonard (1992: 5) states, “The trouble is that we have few, if any maps to guide us on the journey or show us how to find the path…” Assumptions from previous decades that used to increase stress associated with rearing a child with Down syndrome would negatively impact on individual family members and the family unit as such. This has made way for the growing consensus that it is not necessarily the norm. Whilst some families have trouble in adapting to the increased stress, other families adjust easier and even thrive. Successful adaptation seems more likely in resilient families who enjoy high levels of parental well-being and strong relationship bonds. Findings of this qualitative research study confirm that unresolved marital strains are more likely to result in divorce as opposed to the birth of their child with Down syndrome. Correspondingly, siblings of children with Down syndrome reported mostly positive impact than negated opportunities to participate in a normal childhood. My motivation for this research was to explore the nature of challenges faced by modern families and to provide mechanisms to facilitate positive adaptation for the family and aid vii inclusion of the child with Down syndrome into school and greater society. Recommendations are also presented for the medical professionals who, ironically, have proved to be the last people parents want to go for support, owing mostly to their decidedly objectionable treatment of parents; as well as the generally uninformed public, who seldom understand or support attempts of parents to include and expose their child to everyday experiences. In conclusion, I summarize: Should it be that I may influence but one person to see persons with Down syndrome for the potential that they hold instead of the associated problems of their condition, this would afford me the satisfaction and contentment knowing that I have succeeded in making a positive contribution to their plight. I would have successfully portrayed the families for the ordinary people they are with anticipations, aspirations and anxieties, but later tasting the elation of being empowered, and the resultant enjoyment and pride of the achievements of their extraordinary “starfish” child. The simple story below explains it all. A little boy was walking on the beach when he noticed scores of starfish washed onto the beach by the previous night’s high tide. He curiously watched as an old man bent down, came up slowly and tossed one starfish after the other into the surf. He went closer to investigate. “Excuse me, sir, what are you doing?” he enquired. The old man said: “I am throwing the starfish back into the ocean before they die, my boy…come, lend a hand”. The boy looked up and down the beach at the hundreds of starfish scattered along the shoreline. “But there’s too many…” said the boy, “it’ll make no difference!” The old man smiled, bent down, picked up another starfish, and carefully tossing it into the clear blue water, he replied, “…It makes a difference to this one…”
- Full Text:
- Date Issued: 2011
An evaluation of the factors affecting student success at a South African higher education institution : implications for management
- Authors: Watkiss, Sheralyn Ann
- Date: 2011
- Subjects: Education, Higher -- South Africa , College dropout -- Prevention , Management -- Education (Higher) -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:8817 , http://hdl.handle.net/10948/d1018826
- Description: The context of this study centres on Higher Education in South Africa, the role that this sector plays in terms of economic development and the implications that face Institutional management in retaining students in the Higher Education system. Central to this study is the notion that student development theory can be used as a basis towards understanding the customers of Higher Education, how to better serve the customers needs and finally, retain students in the system through more effective management practices. The education sector is growing at an increasingly rapid rate as a result of strategic goals of countries and organisations such as the United Nations promoting the notion of education for all people (Altbach, Reisberg & Rumbley, 2009). The aim of the strategic goals adopted by developing countries in particular is to enhance the human capital or skills and knowledge of its people since education is a known contributor towards economic, social and political development. Higher Education in particular is known to contribute towards the human capital and economic development of a country. The Higher Education sector in South Africa for instance contributes approximately 1.5 percent to the country‟s gross domestic product (GDP), significantly higher than other industry sectors (apart from gold and agriculture) in the country (van Heerden, Bohlmann, Giesecke, Makochekanwa, & Roos, 2007). Figure 1.1 provides a context of the relevant importance of the higher education sector towards economic growth.
- Full Text:
- Date Issued: 2011
- Authors: Watkiss, Sheralyn Ann
- Date: 2011
- Subjects: Education, Higher -- South Africa , College dropout -- Prevention , Management -- Education (Higher) -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:8817 , http://hdl.handle.net/10948/d1018826
- Description: The context of this study centres on Higher Education in South Africa, the role that this sector plays in terms of economic development and the implications that face Institutional management in retaining students in the Higher Education system. Central to this study is the notion that student development theory can be used as a basis towards understanding the customers of Higher Education, how to better serve the customers needs and finally, retain students in the system through more effective management practices. The education sector is growing at an increasingly rapid rate as a result of strategic goals of countries and organisations such as the United Nations promoting the notion of education for all people (Altbach, Reisberg & Rumbley, 2009). The aim of the strategic goals adopted by developing countries in particular is to enhance the human capital or skills and knowledge of its people since education is a known contributor towards economic, social and political development. Higher Education in particular is known to contribute towards the human capital and economic development of a country. The Higher Education sector in South Africa for instance contributes approximately 1.5 percent to the country‟s gross domestic product (GDP), significantly higher than other industry sectors (apart from gold and agriculture) in the country (van Heerden, Bohlmann, Giesecke, Makochekanwa, & Roos, 2007). Figure 1.1 provides a context of the relevant importance of the higher education sector towards economic growth.
- Full Text:
- Date Issued: 2011
Diet of largemouth bass, Micropterus salmoides (Centrarchidae), an invasive alien in the lower reaches of an Eastern Cape river, South Africa.
- Wasserman, Ryan J, Strydom, Nadine A, Weyl, Olaf L F
- Authors: Wasserman, Ryan J , Strydom, Nadine A , Weyl, Olaf L F
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443325 , vital:74108 , https://hdl.handle.net/10520/EJC18195
- Description: Largemouth bass (Micropterus salmoides) have been introduced to many South African river systems where they become invasive and pose a threat to native biota. The diets of small (32-138 mm TL) and large (192-448 mm TL) sized bass were analysed and compared in a marine fish nursery area in the lower Kowie River on the warm temperate coast of South Africa over a one-year period from March 2009 to February 2010. Dietary differences were detected between the two size groups. Amphipod sp. (% index of relative importance (IRI) = 69.2) and dipterans (Insecta) (%IRI = 21.9) dominated gut contents of small bass while larger bass preyed mostly on odonates (Insecta) (%IRI = 16.3) and the brachyuran Potamonautes sidneyi (%IRI = 80.0). Fish prey was of low importance during this study but comparisons with previous work on the lower Kowie River showed that when the river is flowing, young marine fish recruiting into the freshwater from the estuary become important prey items. These data suggest that in the lower Kowie River bass utilize invertebrate prey at low fish prey abundance and opportunistically feed on migrant fish when these are available.
- Full Text:
- Date Issued: 2011
- Authors: Wasserman, Ryan J , Strydom, Nadine A , Weyl, Olaf L F
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443325 , vital:74108 , https://hdl.handle.net/10520/EJC18195
- Description: Largemouth bass (Micropterus salmoides) have been introduced to many South African river systems where they become invasive and pose a threat to native biota. The diets of small (32-138 mm TL) and large (192-448 mm TL) sized bass were analysed and compared in a marine fish nursery area in the lower Kowie River on the warm temperate coast of South Africa over a one-year period from March 2009 to February 2010. Dietary differences were detected between the two size groups. Amphipod sp. (% index of relative importance (IRI) = 69.2) and dipterans (Insecta) (%IRI = 21.9) dominated gut contents of small bass while larger bass preyed mostly on odonates (Insecta) (%IRI = 16.3) and the brachyuran Potamonautes sidneyi (%IRI = 80.0). Fish prey was of low importance during this study but comparisons with previous work on the lower Kowie River showed that when the river is flowing, young marine fish recruiting into the freshwater from the estuary become important prey items. These data suggest that in the lower Kowie River bass utilize invertebrate prey at low fish prey abundance and opportunistically feed on migrant fish when these are available.
- Full Text:
- Date Issued: 2011
A comparison of three techniques for fluorochrome marking of juvenile Clarias gariepinus otoliths
- Wartenberg, Reece, Booth, Anthony J, Weyl, Olaf L F
- Authors: Wartenberg, Reece , Booth, Anthony J , Weyl, Olaf L F
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123520 , vital:35450 , https://doi.10.3377/004.046.0119
- Description: African sharptooth catfish, Clarias gariepinus (Burchell 1822), is widely distributed with a natural range that extends from southern Turkey to the Orange River, South Africa (Skelton 2001). In addition to translocations within its southerly range (Cambray 2003), Cambray (2005) noted that as a result of poor aquaculture practices and introductions from a number of unknown sources, C. gariepinus has now invaded South America, Europe, Asia, and Australia. Its life history characteristics include a fast growth rate to a maximum length of 1300mmtotal length (TL) (Bruton 1976), a high fecundity, an omnivorous diet and the ability to breathe air (de Moor & Bruton 1988; Cambray 2003). Understanding the biology and population dynamics of this invader would assist in its management and possibly eradication.
- Full Text:
- Date Issued: 2011
- Authors: Wartenberg, Reece , Booth, Anthony J , Weyl, Olaf L F
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123520 , vital:35450 , https://doi.10.3377/004.046.0119
- Description: African sharptooth catfish, Clarias gariepinus (Burchell 1822), is widely distributed with a natural range that extends from southern Turkey to the Orange River, South Africa (Skelton 2001). In addition to translocations within its southerly range (Cambray 2003), Cambray (2005) noted that as a result of poor aquaculture practices and introductions from a number of unknown sources, C. gariepinus has now invaded South America, Europe, Asia, and Australia. Its life history characteristics include a fast growth rate to a maximum length of 1300mmtotal length (TL) (Bruton 1976), a high fecundity, an omnivorous diet and the ability to breathe air (de Moor & Bruton 1988; Cambray 2003). Understanding the biology and population dynamics of this invader would assist in its management and possibly eradication.
- Full Text:
- Date Issued: 2011