'Groenvlei' farm, on Great Berg River
- Authors: Skead, C J (Cuthbert John)
- Date: 199u
- Subjects: Plants -- South Africa -- Eastern Cape
- Type: still image
- Identifier: vital:12751 , http://hdl.handle.net/10962/d1014452
- Description: Afternoon sunset.
- Full Text: false
- Date Issued: 199u
- Authors: Skead, C J (Cuthbert John)
- Date: 199u
- Subjects: Plants -- South Africa -- Eastern Cape
- Type: still image
- Identifier: vital:12751 , http://hdl.handle.net/10962/d1014452
- Description: Afternoon sunset.
- Full Text: false
- Date Issued: 199u
'Groenvlei' farm, on Great Berg River
- Authors: Skead, C J (Cuthbert John)
- Date: 199u
- Subjects: Plants -- South Africa -- Eastern Cape
- Type: still image
- Identifier: vital:12750 , http://hdl.handle.net/10962/d1014451
- Description: Afternoon sunset.
- Full Text: false
- Date Issued: 199u
- Authors: Skead, C J (Cuthbert John)
- Date: 199u
- Subjects: Plants -- South Africa -- Eastern Cape
- Type: still image
- Identifier: vital:12750 , http://hdl.handle.net/10962/d1014451
- Description: Afternoon sunset.
- Full Text: false
- Date Issued: 199u
Distribution, habitat associations and conservation of the Eastern Cape rocky Sandelia bainsii (Perciform: Anabantidae) in the Great Fish River system
- Authors: Sifundza, Delsy Sindy
- Date: 2020
- Subjects: Anabantidae -- South Africa -- Great Fish River , Perciformes -- South Africa -- Great Fish River , Labyrinth fishes -- South Africa -- Great Fish River , Fishes -- Effect of human beings on -- South Africa -- Great Fish River , Fish populations -- South Africa -- Great Fish River , Fish declines -- South Africa -- Great Fish River , Fish populations -- Monitoring -- South Africa -- Great Fish River , Anabantidae -- Evolution -- South Africa -- Great Fish River , Gene flow , Mitochondrial DNA , Microsatellites (Genetics) , Eastern Cape rocky Sandelia bainsii , Freshwater ecology -- South Africa -- Great Fish River
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/142692 , vital:38102
- Description: In South Africa, freshwater ecosystems are under pressure due to increasing anthropogenic factors degrading river systems. The Cape Fold, the lower Southern Temperate Highveld and the Amatolo – Winterberg Highlands freshwater ecoregions contain some of the heavily impacted river systems in the country. One such river system is the Great Fish River system, which has been affected by anthropogenic modification (hydrological modification, water pollution and invasion by non-native fish species). These modifications have raised conservation concerns on an imperilled anabantid fish, the Eastern Cape rocky Sandelia bainsii that is confined to the Kat and Koonap rivers, which are tributaries of the Great Fish River. Historically, the species was reportedly common and abundant, with a range spanning across seven river systems (Kowie, Great Fish, Keiskamma, Igoda, Gxulu, Buffalo and Nahoon rivers) in the Eastern Cape Province. However, surveys have indicated that the species has experienced decline in population size and distribution range, with localised extirpations being reported. This resulted in its listing on the IUCN Red List of threatened species as Endangered. The proposed shale gas exploration and potential infrastructure development in the Karoo basin, which encompasses the headwaters of the Kat River, represent a potential future threat to the remnant populations of this species. The aim of the present study was to review the past and present distribution range of S. bainsii, determine the habitat associations and assess the conservation of S. bainsii in the Great Fish River system. This information is essential for informing conservation and management decisions for this species in the Great Fish River system. This study undertook a comprehensive survey of the Kat and the Koonap rivers in 2017, and augmented this information with data from more recent surveys that were conducted from 2009 - 2014 to map the distributions freshwater fishes in the Great Fish River system. Data from these recent surveys (2009 – 2017) were compared with historical records (1961 – 2005) obtained from the South African Institute for Aquatic Biodiversity to evaluate changes in distribution patterns of S. bainsii. Historical records indicated that S. bainsii occurred at 11 localities in the Kat River and three localities in the Koonap River. Data from recent surveys indicated that the species has persisted at these historical localities, except one locality in the Koonap River where no individuals of S. bainsii were captured, despite the use of multiple sampling approaches and gears. Although the species still persists at two of the three historical localities in the Koonap River, the population sizes have considerably declined as the species was reportedly in high abundance at these localities in the 1980s. Factors threatening the continued existence of this species in the Koonap River likely include non-native species, extreme drought conditions and the associated excessive abstraction of water which has resulted in the drying of some of the refugia pools where the species was historically common and abundant. In contrast to the Koonap River, the 2017 survey indicated that in the Kat River, S. bainsii had a similar distribution range compared to historical records. The species occurred at 11 of the 41 localities that were sampled in the Kat River, and the sampled populations consisted of all size classes. Sandelia bainsii occurred with other native fish species in the system, including Labeo umbratus, Enteromius anoplus and Glossogobius callidus. A comparison of historical and recent data indicates that non-native fishes have likely not expanded their ranges in the Kat River. This is likely due to the presence of weirs and dams that have prevented upstream movement of non-native fish species L. aeneus, C. gariepinus and T. sparrmanii which are now abundant in the lower Kat and mainstem Great Fish River. Surveys from the present study indicated that although S. bainsii still persists within the Kat River, there are a number of factors that pose a considerable threat to the continued existence of this species in the Great Fish River system. Chapter 3 evaluated the habitat associations of S. bainsii based on 10 physical and chemical variables and distribution data collected from 30 localities in the Upper Kat River and seven of its tributaries. A non-metric multidimensional scaling model was used to assess the distribution patterns of S. bainsii in relation to environmental variables. Furthermore, a negative binomial generalised linear model (GLM) was used to assess the relationship between the abundance of S. bainsii and environmental variables. Results from the present study indicated that S. bainsii was a habitat generalist as the distribution of this species showed no specific association with any of the habitat variables that were considered in this study. The species occurred in a wide range of habitats, including rocky sections in the upper Kat River and its tributaries as well as the mainstem sections. The GLM however indicated that the abundance of S. bainsii was negatively associated with increasing conductivity. In addition, the Kat River contains multiple weirs of variable sizes. Future studies should therefore evaluate the effects of these weirs on population fragmentation, gene flow and long-term evolutionary potential of S. bainsii through the application of techniques such as mitochondrial DNA and microsatellites.
- Full Text:
- Date Issued: 2020
- Authors: Sifundza, Delsy Sindy
- Date: 2020
- Subjects: Anabantidae -- South Africa -- Great Fish River , Perciformes -- South Africa -- Great Fish River , Labyrinth fishes -- South Africa -- Great Fish River , Fishes -- Effect of human beings on -- South Africa -- Great Fish River , Fish populations -- South Africa -- Great Fish River , Fish declines -- South Africa -- Great Fish River , Fish populations -- Monitoring -- South Africa -- Great Fish River , Anabantidae -- Evolution -- South Africa -- Great Fish River , Gene flow , Mitochondrial DNA , Microsatellites (Genetics) , Eastern Cape rocky Sandelia bainsii , Freshwater ecology -- South Africa -- Great Fish River
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/142692 , vital:38102
- Description: In South Africa, freshwater ecosystems are under pressure due to increasing anthropogenic factors degrading river systems. The Cape Fold, the lower Southern Temperate Highveld and the Amatolo – Winterberg Highlands freshwater ecoregions contain some of the heavily impacted river systems in the country. One such river system is the Great Fish River system, which has been affected by anthropogenic modification (hydrological modification, water pollution and invasion by non-native fish species). These modifications have raised conservation concerns on an imperilled anabantid fish, the Eastern Cape rocky Sandelia bainsii that is confined to the Kat and Koonap rivers, which are tributaries of the Great Fish River. Historically, the species was reportedly common and abundant, with a range spanning across seven river systems (Kowie, Great Fish, Keiskamma, Igoda, Gxulu, Buffalo and Nahoon rivers) in the Eastern Cape Province. However, surveys have indicated that the species has experienced decline in population size and distribution range, with localised extirpations being reported. This resulted in its listing on the IUCN Red List of threatened species as Endangered. The proposed shale gas exploration and potential infrastructure development in the Karoo basin, which encompasses the headwaters of the Kat River, represent a potential future threat to the remnant populations of this species. The aim of the present study was to review the past and present distribution range of S. bainsii, determine the habitat associations and assess the conservation of S. bainsii in the Great Fish River system. This information is essential for informing conservation and management decisions for this species in the Great Fish River system. This study undertook a comprehensive survey of the Kat and the Koonap rivers in 2017, and augmented this information with data from more recent surveys that were conducted from 2009 - 2014 to map the distributions freshwater fishes in the Great Fish River system. Data from these recent surveys (2009 – 2017) were compared with historical records (1961 – 2005) obtained from the South African Institute for Aquatic Biodiversity to evaluate changes in distribution patterns of S. bainsii. Historical records indicated that S. bainsii occurred at 11 localities in the Kat River and three localities in the Koonap River. Data from recent surveys indicated that the species has persisted at these historical localities, except one locality in the Koonap River where no individuals of S. bainsii were captured, despite the use of multiple sampling approaches and gears. Although the species still persists at two of the three historical localities in the Koonap River, the population sizes have considerably declined as the species was reportedly in high abundance at these localities in the 1980s. Factors threatening the continued existence of this species in the Koonap River likely include non-native species, extreme drought conditions and the associated excessive abstraction of water which has resulted in the drying of some of the refugia pools where the species was historically common and abundant. In contrast to the Koonap River, the 2017 survey indicated that in the Kat River, S. bainsii had a similar distribution range compared to historical records. The species occurred at 11 of the 41 localities that were sampled in the Kat River, and the sampled populations consisted of all size classes. Sandelia bainsii occurred with other native fish species in the system, including Labeo umbratus, Enteromius anoplus and Glossogobius callidus. A comparison of historical and recent data indicates that non-native fishes have likely not expanded their ranges in the Kat River. This is likely due to the presence of weirs and dams that have prevented upstream movement of non-native fish species L. aeneus, C. gariepinus and T. sparrmanii which are now abundant in the lower Kat and mainstem Great Fish River. Surveys from the present study indicated that although S. bainsii still persists within the Kat River, there are a number of factors that pose a considerable threat to the continued existence of this species in the Great Fish River system. Chapter 3 evaluated the habitat associations of S. bainsii based on 10 physical and chemical variables and distribution data collected from 30 localities in the Upper Kat River and seven of its tributaries. A non-metric multidimensional scaling model was used to assess the distribution patterns of S. bainsii in relation to environmental variables. Furthermore, a negative binomial generalised linear model (GLM) was used to assess the relationship between the abundance of S. bainsii and environmental variables. Results from the present study indicated that S. bainsii was a habitat generalist as the distribution of this species showed no specific association with any of the habitat variables that were considered in this study. The species occurred in a wide range of habitats, including rocky sections in the upper Kat River and its tributaries as well as the mainstem sections. The GLM however indicated that the abundance of S. bainsii was negatively associated with increasing conductivity. In addition, the Kat River contains multiple weirs of variable sizes. Future studies should therefore evaluate the effects of these weirs on population fragmentation, gene flow and long-term evolutionary potential of S. bainsii through the application of techniques such as mitochondrial DNA and microsatellites.
- Full Text:
- Date Issued: 2020
Taxonomic, ecological and biogeographic re-evaluation of temperate stream fishes in Southern Africa: a case study of the enteromius anoplus complex
- Authors: Kambikambi, Manda Juliet
- Date: 2021-10-29
- Subjects: Stream ecology South Africa , Barbs (Fish) Ecology South Africa Cape Fold Belt , Barbs (Fish) Ecology South Africa Highveld (Region) , Barbs (Fish) Ecology South Africa Amathole District Municipality , Biotic communities South Africa , Fishes Classification , Cryptic species , Chubbyhead barb
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/191023 , vital:45051 , 10.21504/10962/191023
- Description: Worldwide, cryptic species, which comprise two or more distinct species that are classified as one due to their morphological similarity, are more common than previously thought. In South Africa, the chubbyhead barb, Enteromius anoplus (Weber, 1897), is the most widespread freshwater fish species. The widespread occurrence of this species across different river basins raised questions on its taxonomic status due to the likely occurrence of hidden diversity. This further raised the need to evaluate the ecological patterns associated with likely occurrence of such hidden diversity. Phylogenetic analyses of the cytochrome b gene of E. anoplus populations across South Africa revealed the occurrence of four genetically distinct species. These findings supported the restoration Enteromius cernuus (Barnard 1943) stat. rev. from the Olifants River system; the restoration of Enteromius anoplus sensu stricto (Weber 1897) stat. rev. from the Gouritz River system; the redescription of Enteromius oraniensis (Barnard 1943) stat. rev. from the Orange River system; and the description of a new species, Enteromius mandelai sp. nov. from the Eastern Cape rivers. Analyses of morphometric and meristic data revealed that these species were differentiated based on barbel length and number of lateral line scales. Ecological studies on Enteromius mandelai were conducted within headwater streams of major river systems in the Eastern Cape region. These headwater streams had different catchment characteristics ranging from near-natural to anthropogenically-perturbed mainly due to agriculture-related disturbances and invasion of riparian zones by non-native plants. Stable isotope analysis provided evidence of trophic plasticity for E. mandelai across the different headwater streams. Specifically, E. mandelai exhibited large isotopic niches in agriculture-disturbed headwater streams, whereas small isotopic niches were observed in headwater streams invaded by non-native plants. Because of the evidence of trophic plasticity for E. mandelai, this study further hypothesized that this species would exhibit variable environmental niche patterns related to its distribution, abundance and the presence of contra-specifics due to different abiotic factors across its range. Enteromius mandelai was generally most abundant at sites with high total dissolved solids and sand substratum, which was characteristic of large pool habitats, and least abundant at sites with high turbidity. In the Great Fish River, E. mandelai occurred as the only species in most headwater sites, whereas in the Keiskamma and Buffalo River systems, it co-occurred with Amatolacypris trevelyani and Sandelia bainsii. Enteromius mandelai was, nevertheless, found to be ubiquitous together with having wide environmental niches, and exhibited no discernible patterns in its habitat associations. The taxonomic re-evaluation of the E. anoplus complex, which provided evidence of the existence of new species, has implications for the biogeographic zonation of the ichthyofauna of the Cape Fold Ecoregion (CFE), Amathole-Winterberg Highlands Ecoregion (AWHE) and the Southern Temperate Highveld Ecoregion (STHE). For example, the currently recognised southern limit of the STHE, which encompasses the AWHE, is based on the occurrence of E. anoplus, Enteromius pallidus and Labeo umbratus. However, evidence from this and other recent studies indicate the occurrence of either new species or distinct lineages in the southern-most section of the STHE, which is consistent with the patterns observed in the CFE. Comparison of taxonomic composition showed that species in the eastern part of the CFE were similar to species in the AWHE and the southern-most section of the STHE. Because of the close affinities among most of the new taxa in these regions, this study proposes that the current delimitation of the CFE should be reviewed by extending it to include the AWHE and sections of the STHE. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Kambikambi, Manda Juliet
- Date: 2021-10-29
- Subjects: Stream ecology South Africa , Barbs (Fish) Ecology South Africa Cape Fold Belt , Barbs (Fish) Ecology South Africa Highveld (Region) , Barbs (Fish) Ecology South Africa Amathole District Municipality , Biotic communities South Africa , Fishes Classification , Cryptic species , Chubbyhead barb
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/191023 , vital:45051 , 10.21504/10962/191023
- Description: Worldwide, cryptic species, which comprise two or more distinct species that are classified as one due to their morphological similarity, are more common than previously thought. In South Africa, the chubbyhead barb, Enteromius anoplus (Weber, 1897), is the most widespread freshwater fish species. The widespread occurrence of this species across different river basins raised questions on its taxonomic status due to the likely occurrence of hidden diversity. This further raised the need to evaluate the ecological patterns associated with likely occurrence of such hidden diversity. Phylogenetic analyses of the cytochrome b gene of E. anoplus populations across South Africa revealed the occurrence of four genetically distinct species. These findings supported the restoration Enteromius cernuus (Barnard 1943) stat. rev. from the Olifants River system; the restoration of Enteromius anoplus sensu stricto (Weber 1897) stat. rev. from the Gouritz River system; the redescription of Enteromius oraniensis (Barnard 1943) stat. rev. from the Orange River system; and the description of a new species, Enteromius mandelai sp. nov. from the Eastern Cape rivers. Analyses of morphometric and meristic data revealed that these species were differentiated based on barbel length and number of lateral line scales. Ecological studies on Enteromius mandelai were conducted within headwater streams of major river systems in the Eastern Cape region. These headwater streams had different catchment characteristics ranging from near-natural to anthropogenically-perturbed mainly due to agriculture-related disturbances and invasion of riparian zones by non-native plants. Stable isotope analysis provided evidence of trophic plasticity for E. mandelai across the different headwater streams. Specifically, E. mandelai exhibited large isotopic niches in agriculture-disturbed headwater streams, whereas small isotopic niches were observed in headwater streams invaded by non-native plants. Because of the evidence of trophic plasticity for E. mandelai, this study further hypothesized that this species would exhibit variable environmental niche patterns related to its distribution, abundance and the presence of contra-specifics due to different abiotic factors across its range. Enteromius mandelai was generally most abundant at sites with high total dissolved solids and sand substratum, which was characteristic of large pool habitats, and least abundant at sites with high turbidity. In the Great Fish River, E. mandelai occurred as the only species in most headwater sites, whereas in the Keiskamma and Buffalo River systems, it co-occurred with Amatolacypris trevelyani and Sandelia bainsii. Enteromius mandelai was, nevertheless, found to be ubiquitous together with having wide environmental niches, and exhibited no discernible patterns in its habitat associations. The taxonomic re-evaluation of the E. anoplus complex, which provided evidence of the existence of new species, has implications for the biogeographic zonation of the ichthyofauna of the Cape Fold Ecoregion (CFE), Amathole-Winterberg Highlands Ecoregion (AWHE) and the Southern Temperate Highveld Ecoregion (STHE). For example, the currently recognised southern limit of the STHE, which encompasses the AWHE, is based on the occurrence of E. anoplus, Enteromius pallidus and Labeo umbratus. However, evidence from this and other recent studies indicate the occurrence of either new species or distinct lineages in the southern-most section of the STHE, which is consistent with the patterns observed in the CFE. Comparison of taxonomic composition showed that species in the eastern part of the CFE were similar to species in the AWHE and the southern-most section of the STHE. Because of the close affinities among most of the new taxa in these regions, this study proposes that the current delimitation of the CFE should be reviewed by extending it to include the AWHE and sections of the STHE. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2021
- Full Text:
- Date Issued: 2021-10-29
Status of farm dwellers in the Great Kei municipality post implementation of the security tenure act
- Authors: Mfeya, Nontando Hazel
- Date: 2017
- Subjects: Eviction -- South Africa -- Eastern Cape , Land tenure -- South Africa -- Eastern Cape Occupancy (Law) -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/14002 , vital:27381
- Description: The period preceding and after the enactment of ESTA marks an increase in the difficulties faced by the farm dwellers in South Africa. They are still faced with illegal evictions. Their difficulties are marked with loss of land for food farming, loss of work, income and homes. Nevertheless, the introduction of ESTA in 1997 aimed at protecting and restoring the land rights of farm dwellers working on farms. Despite its existence there are still challenges of illegal evictions. This research focuses on difficulties faced by farm workers after the enactment of ESTA and investigate the process and effects of illegal evictions. The thesis adopts a qualitative research methodology that takes the form of a case study on two farms, Killarney farm and Shellford farm, where farm workers experienced evictions. The findings confirm that the farm workers are subject to illegal evictions. The evictions are due to the conversion of agricultural farms to game farming and also due to labour disputes. Poor living conditions are evident and farm owners conduct tacit evictions by imposing restrictions and threatening the farm workers who wish to stay on the farms. This thesis concludes by presenting suggestions that may restrict or put an end to illegal evictions. ESTA needs to be amended in order to ensure the security of farm workers who live on the farms.
- Full Text:
- Date Issued: 2017
Status of farm dwellers in the Great Kei municipality post implementation of the security tenure act
- Authors: Mfeya, Nontando Hazel
- Date: 2017
- Subjects: Eviction -- South Africa -- Eastern Cape , Land tenure -- South Africa -- Eastern Cape Occupancy (Law) -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/14002 , vital:27381
- Description: The period preceding and after the enactment of ESTA marks an increase in the difficulties faced by the farm dwellers in South Africa. They are still faced with illegal evictions. Their difficulties are marked with loss of land for food farming, loss of work, income and homes. Nevertheless, the introduction of ESTA in 1997 aimed at protecting and restoring the land rights of farm dwellers working on farms. Despite its existence there are still challenges of illegal evictions. This research focuses on difficulties faced by farm workers after the enactment of ESTA and investigate the process and effects of illegal evictions. The thesis adopts a qualitative research methodology that takes the form of a case study on two farms, Killarney farm and Shellford farm, where farm workers experienced evictions. The findings confirm that the farm workers are subject to illegal evictions. The evictions are due to the conversion of agricultural farms to game farming and also due to labour disputes. Poor living conditions are evident and farm owners conduct tacit evictions by imposing restrictions and threatening the farm workers who wish to stay on the farms. This thesis concludes by presenting suggestions that may restrict or put an end to illegal evictions. ESTA needs to be amended in order to ensure the security of farm workers who live on the farms.
- Full Text:
- Date Issued: 2017
The geography of the Bedford, Adelaide, Fort Beaufort, Stockenström and Victoria East magisterial districts
- Authors: Childs, Nicol Treloar
- Date: 1972
- Subjects: Eastern Cape (South Africa) -- Geography , Land use, Rural -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:4861 , http://hdl.handle.net/10962/d1006845 , Eastern Cape (South Africa) -- Geography , Land use, Rural -- South Africa -- Eastern Cape
- Description: From introduction: This is a study of the physical landscape, climate, natural vegetation, historical geography and rural land use of the Bedford, Adelaide, Fort Beaufort, Stockenström and Victoria East magisterial districts. These five districts may be regarded as a natural region bounded by the crest of the Amatole-Winterberg range in the north and by the Great Fish River in the west. The southern boundary is a zone of semi-arid scrub bordering the Great Fish River valley. The Ciskei may be regarded as the eastern boundary of the region.
- Full Text:
- Date Issued: 1972
- Authors: Childs, Nicol Treloar
- Date: 1972
- Subjects: Eastern Cape (South Africa) -- Geography , Land use, Rural -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:4861 , http://hdl.handle.net/10962/d1006845 , Eastern Cape (South Africa) -- Geography , Land use, Rural -- South Africa -- Eastern Cape
- Description: From introduction: This is a study of the physical landscape, climate, natural vegetation, historical geography and rural land use of the Bedford, Adelaide, Fort Beaufort, Stockenström and Victoria East magisterial districts. These five districts may be regarded as a natural region bounded by the crest of the Amatole-Winterberg range in the north and by the Great Fish River in the west. The southern boundary is a zone of semi-arid scrub bordering the Great Fish River valley. The Ciskei may be regarded as the eastern boundary of the region.
- Full Text:
- Date Issued: 1972
Negotiating impoverishment: Farm worker responses to displacement following land invasions in Zimbabwe's "Fast Track Land Reform Programme"
- Hartnack, Andrew Michael Carl
- Authors: Hartnack, Andrew Michael Carl
- Date: 2006
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/197076 , vital:45834
- Description: This thesis investigates the impacts of sudden, unplanned, and violent displacement on farm workers such as Frank Juwawo during Zimbabwe’s recent Fast Track Land Reform Programme. It seeks to illustrate how the members of a complex community were differentially impacted by displacement and displayed differing abilities to mitigate the resulting social and economic impoverishment. In order to illuminate this particular displacement scenario, this thesis uses theoretical and analytical tools developed in the field of displacement studies, adapting them to suit the kind of displacement experienced by Zimbabwean farm workers. , Thesis (MA) -- Faculty of Humanities, Anthropology, 2006
- Full Text:
- Date Issued: 2006
- Authors: Hartnack, Andrew Michael Carl
- Date: 2006
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/197076 , vital:45834
- Description: This thesis investigates the impacts of sudden, unplanned, and violent displacement on farm workers such as Frank Juwawo during Zimbabwe’s recent Fast Track Land Reform Programme. It seeks to illustrate how the members of a complex community were differentially impacted by displacement and displayed differing abilities to mitigate the resulting social and economic impoverishment. In order to illuminate this particular displacement scenario, this thesis uses theoretical and analytical tools developed in the field of displacement studies, adapting them to suit the kind of displacement experienced by Zimbabwean farm workers. , Thesis (MA) -- Faculty of Humanities, Anthropology, 2006
- Full Text:
- Date Issued: 2006
Colonisation theory and invasive biota : the Great Fish river, a case history
- Authors: Laurenson, Lawrie Jon Bain
- Date: 1986
- Subjects: Biological invasions -- South Africa -- Great Fish River , Clarias gariepinus , Barbus aeneus , Freshwater ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5338 , http://hdl.handle.net/10962/d1005905 , Biological invasions -- South Africa -- Great Fish River , Clarias gariepinus , Barbus aeneus , Freshwater ecology
- Description: Colonisation theory relative to introduced populations was examined with a view to determining the usefulness of theoretical concepts in the prediction of the success of an invasion by a species. To this end, the Great Fish River, with reference to species introduced by the Orange/Fish Tunnel, was used as a case history. It was concluded that theoretical descriptions of population growth, control and decline are useful only when considering individual ecosystems or species. The highly variable nature of species and environments nullifies attempts to simplify behavioural characteristics into a predictive framework. There is an abundance of terminology associated with introduced organisms and frequently many of these terms are used synonymously. Eleven terms have been defined in this thesis with a view to standardising terminology. Characteristics of species and environments which enhance their susceptibility to invasions by exotic ichthyofauna were discussed and summarised. Distribution data concerning exotic fish introduced into the Great Fish River by the Orange/Fish Tunnel has demonstrated that, with the exception of Clarias gariepinus, all remaining exotics have restricted distributions. Only Barbus aeneus appears to be extending its range down the drainage. Age, Growth, reproduction and condition data support the conclusion that, excluding B. aeneus and C. gariepinus, invasive species in the drainage are not performing well. Of the five invasive species (B. aeneus, Labeo capensis, L. umbratus, Gephyroglanis sclateri and Cyprinus carpio), only two have established populations (B. aeneus· and C. gariepinus). Labeo umbratus and C. carpio were present on the Great Fish River prior to the construction of the tunnel and populations of the species could not be distinguished. It was concluded that there is no evidence to suggest that exotic species introduced into the Great Fish River are having a deleterious effect on indigenous, endangered ichthyofauna. Monitoring of the drainage should be continued to ensure that a danger to indigenous species does not develop.
- Full Text:
- Date Issued: 1986
- Authors: Laurenson, Lawrie Jon Bain
- Date: 1986
- Subjects: Biological invasions -- South Africa -- Great Fish River , Clarias gariepinus , Barbus aeneus , Freshwater ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5338 , http://hdl.handle.net/10962/d1005905 , Biological invasions -- South Africa -- Great Fish River , Clarias gariepinus , Barbus aeneus , Freshwater ecology
- Description: Colonisation theory relative to introduced populations was examined with a view to determining the usefulness of theoretical concepts in the prediction of the success of an invasion by a species. To this end, the Great Fish River, with reference to species introduced by the Orange/Fish Tunnel, was used as a case history. It was concluded that theoretical descriptions of population growth, control and decline are useful only when considering individual ecosystems or species. The highly variable nature of species and environments nullifies attempts to simplify behavioural characteristics into a predictive framework. There is an abundance of terminology associated with introduced organisms and frequently many of these terms are used synonymously. Eleven terms have been defined in this thesis with a view to standardising terminology. Characteristics of species and environments which enhance their susceptibility to invasions by exotic ichthyofauna were discussed and summarised. Distribution data concerning exotic fish introduced into the Great Fish River by the Orange/Fish Tunnel has demonstrated that, with the exception of Clarias gariepinus, all remaining exotics have restricted distributions. Only Barbus aeneus appears to be extending its range down the drainage. Age, Growth, reproduction and condition data support the conclusion that, excluding B. aeneus and C. gariepinus, invasive species in the drainage are not performing well. Of the five invasive species (B. aeneus, Labeo capensis, L. umbratus, Gephyroglanis sclateri and Cyprinus carpio), only two have established populations (B. aeneus· and C. gariepinus). Labeo umbratus and C. carpio were present on the Great Fish River prior to the construction of the tunnel and populations of the species could not be distinguished. It was concluded that there is no evidence to suggest that exotic species introduced into the Great Fish River are having a deleterious effect on indigenous, endangered ichthyofauna. Monitoring of the drainage should be continued to ensure that a danger to indigenous species does not develop.
- Full Text:
- Date Issued: 1986
Distribution and conservation status assessment of the freshwater fishes in the Krom River system in the Eastern Cape Province, South Africa
- Authors: Mthombeni, Annah
- Date: 2023-03-29
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/422303 , vital:71929
- Description: The Cape Fold Ecoregion (CFE) contains the highest number of endemic freshwater fishes in Africa, south of the Zambezi River system. The CFE’s unique fish fauna has, however, suffered severe decline in historical distribution ranges and population sizes due to multiple impacts, with the two main threats being introduced invasive piscivores and habitat degradation. Growing evidence shows that biodiversity is being lost at unprecedented levels due to increased human pressure and demand for limited resources. Future projections also indicate high extinction risk, particularly for freshwater ecosystems, as a result of global climate change. Yet for many regions, including the CFE, there is still limited biodiversity knowledge to guide decision making processes. The Krom River system in the eastern Cape Fold Ecoregion (CFE) contains three native freshwater fish species. These are Pseudobarbus senticeps, which was recently revalidated, Sandelia capensis and a galaxiid lineage currently informally referred to as Galaxias zebratus sp. ‘Joubertina’. Two of these taxa are listed under threatened categories of the International Union for Conservation of Nature (IUCN). These are P. senticeps, which is listed as Critically Endangered and Galaxias zebratus sp. ‘Joubertina’, which is listed as Endangered. Although S. capensis is currently listed as Data Deficient, the most recent information indicates that the species comprises three allopatric lineages, with the Krom River population belonging to a lineage that is distributed across a number of river systems on the south coast. Two non-native fishes, Micropterus salmoides and Lepomis macrochirus, have also been introduced into this river system. Updated information on distribution patterns and habitat utilisation is required to guide authorities to develop effective management plans and conservation of the threatened fishes of the Krom River system. The aim of this study was to determine the current distribution of the fishes of the Krom River system and to provide recommendations for in situ conservation measures to protect remnant populations and promote recovery and range expansion of the native fishes. The primary objective of the study was to use historical and present data to map the distributions patterns. Data on the distribution of the fishes of the Krom River system were obtained from various sources, including the NRF-SAIAB database, studies published in peer reviewed literature and unpublished reports. Systematic sampling was conducted in the Krom River system and several of its tributaries to provide a snapshot of the current distribution of both native and non-native fishes in this system at the time of this study. The presence of instream physical barriers was recorded, and habitat and water quality were visually assessed. Only four species of freshwater fishes were recorded during the surveys. These were two native species, the Krom River redfin P. senticeps and the Cape kurper Sandelia capensis, and two introduced species, the black bass M. salmoides and bluegill sunfish L. macrochirus. Pseudobarbus senticeps was the most common and widely distributed species in the system, and was recorded at 20 localities (four mainstem and 16 tributary localities). Sandelia capensis was less common and was recorded at only eight localities (four mainstem and four tributary localities). These two native species co-occurred at all the eight localities where S. capensis was recorded, but P. senticeps was always more abundant than Sandelia. Micropterus salmoides was recorded at six localities (four mainstem and 2 tributary localities) while L. macrochirus was recorded at five localities (four mainstem and one off-stream dam site). Native fishes were not recorded at sites where non-native fishes were present except at two localities in the Wit Els River where juvenile M. salmoides were found amongst the native fish samples. However, unlike the other localities where all size classes (i.e., young of the year, juveniles, subadults and adults) were present, only adult redfins were found in the Wit Els River where juveniles of largemouth bass occurred. A comparison of the past and present distribution patterns of the native fishes indicates a considerable decline in distribution range, and remnant populations are now fragmented compared to past observations. The major threats and impacts on the Krom River system are the presence of non-native piscivores, construction of instream physical barriers, and agricultural activities. The information from this study could form a basis for establishing long-term conservation measures that should focus on preventing the spread of non-native fishes, and rehabilitating critical habitats for the future persistence of remnant populations of native fishes. The study also evaluated the implications of incomplete taxonomy on conservation status assessments and prioritisation, by evaluating case studies of species complexes of freshwater fishes whose taxonomy has been recently resolved, as well as two complexes with lineages that await formal recognition as distinct species. The aim was to demonstrate how incomplete knowledge of taxonomy affects the assessment of extinction risk and can potentially misdirect conservation prioritisation. Specifically, the study examined how change in taxonomy or recognition of undescribed genetic lineages in faunal listings affects range size and IUCN Red List risk category. The study taxa were Pseudobarbus afer sensu lato (sl), Enteromius anoplus sl, Amphilius natalensis sl, Sandelia capensis and S. bainsii, and the study assessed the species complexes as Least Concern or Near Threatened. The majority of these taxonomically revised species and genetic lineages were determined to be Critically Endangered (CR), Endangered (EN) and Vulnerable (VU), as the extent of occurrence was estimated to be < 100 km2; < 5000 km2 and < 20 000 km2 respectively. The species and lineages have been observed in fewer than ten locations, and the populations have been observed to be in decline. The results of this study indicate that the current taxonomic status of the native species in the Krom River system obscures the diversity of these fishes and affects conclusions for conservation assessments. Findings from this preliminary assessment highlight the need for advancing taxonomic knowledge through accurate delimitation of species boundaries, particularly within , Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries Science, 2023
- Full Text:
- Date Issued: 2023-03-29
- Authors: Mthombeni, Annah
- Date: 2023-03-29
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/422303 , vital:71929
- Description: The Cape Fold Ecoregion (CFE) contains the highest number of endemic freshwater fishes in Africa, south of the Zambezi River system. The CFE’s unique fish fauna has, however, suffered severe decline in historical distribution ranges and population sizes due to multiple impacts, with the two main threats being introduced invasive piscivores and habitat degradation. Growing evidence shows that biodiversity is being lost at unprecedented levels due to increased human pressure and demand for limited resources. Future projections also indicate high extinction risk, particularly for freshwater ecosystems, as a result of global climate change. Yet for many regions, including the CFE, there is still limited biodiversity knowledge to guide decision making processes. The Krom River system in the eastern Cape Fold Ecoregion (CFE) contains three native freshwater fish species. These are Pseudobarbus senticeps, which was recently revalidated, Sandelia capensis and a galaxiid lineage currently informally referred to as Galaxias zebratus sp. ‘Joubertina’. Two of these taxa are listed under threatened categories of the International Union for Conservation of Nature (IUCN). These are P. senticeps, which is listed as Critically Endangered and Galaxias zebratus sp. ‘Joubertina’, which is listed as Endangered. Although S. capensis is currently listed as Data Deficient, the most recent information indicates that the species comprises three allopatric lineages, with the Krom River population belonging to a lineage that is distributed across a number of river systems on the south coast. Two non-native fishes, Micropterus salmoides and Lepomis macrochirus, have also been introduced into this river system. Updated information on distribution patterns and habitat utilisation is required to guide authorities to develop effective management plans and conservation of the threatened fishes of the Krom River system. The aim of this study was to determine the current distribution of the fishes of the Krom River system and to provide recommendations for in situ conservation measures to protect remnant populations and promote recovery and range expansion of the native fishes. The primary objective of the study was to use historical and present data to map the distributions patterns. Data on the distribution of the fishes of the Krom River system were obtained from various sources, including the NRF-SAIAB database, studies published in peer reviewed literature and unpublished reports. Systematic sampling was conducted in the Krom River system and several of its tributaries to provide a snapshot of the current distribution of both native and non-native fishes in this system at the time of this study. The presence of instream physical barriers was recorded, and habitat and water quality were visually assessed. Only four species of freshwater fishes were recorded during the surveys. These were two native species, the Krom River redfin P. senticeps and the Cape kurper Sandelia capensis, and two introduced species, the black bass M. salmoides and bluegill sunfish L. macrochirus. Pseudobarbus senticeps was the most common and widely distributed species in the system, and was recorded at 20 localities (four mainstem and 16 tributary localities). Sandelia capensis was less common and was recorded at only eight localities (four mainstem and four tributary localities). These two native species co-occurred at all the eight localities where S. capensis was recorded, but P. senticeps was always more abundant than Sandelia. Micropterus salmoides was recorded at six localities (four mainstem and 2 tributary localities) while L. macrochirus was recorded at five localities (four mainstem and one off-stream dam site). Native fishes were not recorded at sites where non-native fishes were present except at two localities in the Wit Els River where juvenile M. salmoides were found amongst the native fish samples. However, unlike the other localities where all size classes (i.e., young of the year, juveniles, subadults and adults) were present, only adult redfins were found in the Wit Els River where juveniles of largemouth bass occurred. A comparison of the past and present distribution patterns of the native fishes indicates a considerable decline in distribution range, and remnant populations are now fragmented compared to past observations. The major threats and impacts on the Krom River system are the presence of non-native piscivores, construction of instream physical barriers, and agricultural activities. The information from this study could form a basis for establishing long-term conservation measures that should focus on preventing the spread of non-native fishes, and rehabilitating critical habitats for the future persistence of remnant populations of native fishes. The study also evaluated the implications of incomplete taxonomy on conservation status assessments and prioritisation, by evaluating case studies of species complexes of freshwater fishes whose taxonomy has been recently resolved, as well as two complexes with lineages that await formal recognition as distinct species. The aim was to demonstrate how incomplete knowledge of taxonomy affects the assessment of extinction risk and can potentially misdirect conservation prioritisation. Specifically, the study examined how change in taxonomy or recognition of undescribed genetic lineages in faunal listings affects range size and IUCN Red List risk category. The study taxa were Pseudobarbus afer sensu lato (sl), Enteromius anoplus sl, Amphilius natalensis sl, Sandelia capensis and S. bainsii, and the study assessed the species complexes as Least Concern or Near Threatened. The majority of these taxonomically revised species and genetic lineages were determined to be Critically Endangered (CR), Endangered (EN) and Vulnerable (VU), as the extent of occurrence was estimated to be < 100 km2; < 5000 km2 and < 20 000 km2 respectively. The species and lineages have been observed in fewer than ten locations, and the populations have been observed to be in decline. The results of this study indicate that the current taxonomic status of the native species in the Krom River system obscures the diversity of these fishes and affects conclusions for conservation assessments. Findings from this preliminary assessment highlight the need for advancing taxonomic knowledge through accurate delimitation of species boundaries, particularly within , Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries Science, 2023
- Full Text:
- Date Issued: 2023-03-29
Establishment and impact of the sap-sucking mirid, Falconia intermedia (Distant) (Hemiptera: Miridae) on Lantana camara (Verbenaceae) varieties in the Eastern Cape Province, South Africa
- Heshula, Unathi-Nkosi Lelethu Peter
- Authors: Heshula, Unathi-Nkosi Lelethu Peter
- Date: 2005
- Subjects: Lantana camara -- South Africa -- Eastern Cape , Biological pest control agents -- South Africa -- Eastern Cape , Hemiptera -- South Africa -- Eastern Cape , Miridae -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5832 , http://hdl.handle.net/10962/d1008085
- Description: The biological control of the weedy complex Lantana camara (L.) (Verbenaceae) has been ongoing in South Africa for over 40 years. Despite this, the weed is still not under sufficient control and continues to invade new territories in the country. The biological control programme needs to be bolstered with releases of new and potentially damaging biological control agents. A promising biological control agent endemic to Central America, Falconia intermedia (Distant) (Hemiptera: Miridae), was imported into quarantine from Jamaica in 1994. This agent was released on sites in KwaZulu-Natal and Limpopo provinces of South Africa in 1999. Even though it initially established and damaged L. camara, populations died out at most of the release sites. As varietal difference and adverse climate have been cited as the reason for non-establishment and ineffective control in L. camara biocontrol programmes worldwide, this study attempts to investigate the role that these two factors play in this weed herbivore relationship. Laboratory no-choice trials were conducted to determine the varietal performance of F intermedia, among five Eastern Cape varieties of the weed from East London, Whitney Farm, Heather Glen Farm, Port Alfred and Lyndhurst Farm, and a variety from the Plant Protection Research Institute (PPRI), Pretoria. However, there were differences in performance as the adult mirids performed better on white-pink varieties from Whitney Farm and Heather Glen Farm. To test varietal preference in field conditions, field releases of F intermedia were also made at East London, Whitney Farm, Heather Glen Farm, Port Alfred and Lyndhurst Farm. Post release evaluations were conducted monthly for two years (2002 and 2003). The insect established at East London and Whitney Farm, both of which have white-pink varieties. Insect populations quickly died out at the Lyndhurst Farm and Port Alfred sites, which have dark pink varieties. It is suggested that field conditions may have resulted in poor plant quality and led indirectly to varietal preference, and to non-establishment at these two sites. With the onset of cooler weather, populations disappeared at Heather Glen Farm. This suggested that F. intermedia was suitable for release in more subtropical areas within South Africa where climatic conditions would be suitable throughout the year. The mirid performed well at Whitney Farm, resulting in significant reduction in plant growth parameters such as height and percentage cover, and increasing the cover of other flora growing beneath L. camara plants. Finally, ways to improve the efficacy of this agent are considered in an effort towards better control of L. camara in South Africa.
- Full Text:
- Date Issued: 2005
- Authors: Heshula, Unathi-Nkosi Lelethu Peter
- Date: 2005
- Subjects: Lantana camara -- South Africa -- Eastern Cape , Biological pest control agents -- South Africa -- Eastern Cape , Hemiptera -- South Africa -- Eastern Cape , Miridae -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5832 , http://hdl.handle.net/10962/d1008085
- Description: The biological control of the weedy complex Lantana camara (L.) (Verbenaceae) has been ongoing in South Africa for over 40 years. Despite this, the weed is still not under sufficient control and continues to invade new territories in the country. The biological control programme needs to be bolstered with releases of new and potentially damaging biological control agents. A promising biological control agent endemic to Central America, Falconia intermedia (Distant) (Hemiptera: Miridae), was imported into quarantine from Jamaica in 1994. This agent was released on sites in KwaZulu-Natal and Limpopo provinces of South Africa in 1999. Even though it initially established and damaged L. camara, populations died out at most of the release sites. As varietal difference and adverse climate have been cited as the reason for non-establishment and ineffective control in L. camara biocontrol programmes worldwide, this study attempts to investigate the role that these two factors play in this weed herbivore relationship. Laboratory no-choice trials were conducted to determine the varietal performance of F intermedia, among five Eastern Cape varieties of the weed from East London, Whitney Farm, Heather Glen Farm, Port Alfred and Lyndhurst Farm, and a variety from the Plant Protection Research Institute (PPRI), Pretoria. However, there were differences in performance as the adult mirids performed better on white-pink varieties from Whitney Farm and Heather Glen Farm. To test varietal preference in field conditions, field releases of F intermedia were also made at East London, Whitney Farm, Heather Glen Farm, Port Alfred and Lyndhurst Farm. Post release evaluations were conducted monthly for two years (2002 and 2003). The insect established at East London and Whitney Farm, both of which have white-pink varieties. Insect populations quickly died out at the Lyndhurst Farm and Port Alfred sites, which have dark pink varieties. It is suggested that field conditions may have resulted in poor plant quality and led indirectly to varietal preference, and to non-establishment at these two sites. With the onset of cooler weather, populations disappeared at Heather Glen Farm. This suggested that F. intermedia was suitable for release in more subtropical areas within South Africa where climatic conditions would be suitable throughout the year. The mirid performed well at Whitney Farm, resulting in significant reduction in plant growth parameters such as height and percentage cover, and increasing the cover of other flora growing beneath L. camara plants. Finally, ways to improve the efficacy of this agent are considered in an effort towards better control of L. camara in South Africa.
- Full Text:
- Date Issued: 2005
Determinants of rural households’ diversification of livelihood strategies: a case of Intsika Yethu farmers of the Eastern Cape province, South Africa
- Authors: Munhenga, Daniel
- Date: 2014
- Subjects: Sustainable development -- South Africa -- Eastern Cape , Economic development projects -- South Africa -- Eastern Cape , Farm management -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc Agric (Agricultural Economics)
- Identifier: vital:11220 , http://hdl.handle.net/10353/d1019818 , Sustainable development -- South Africa -- Eastern Cape , Economic development projects -- South Africa -- Eastern Cape , Farm management -- South Africa -- Eastern Cape
- Description: Despite the continuing perceived economic centrality of agriculture in Intsika Yethu local municipality, rural households engage and pursue diverse non-farm livelihood activities to cope with diverse challenges and risks such as drought. This study assessed the importance of existing livelihood strategies adopted by the different rural households in Intsika Yethu; the link between households’ ownership and access to different ‘assets’; factors determining households’ ability to adopt certain livelihood strategies in the area. A survey of 120 households in six administrative areas and informal discussions with key informants were used to collect demographic data, data on socio-economic activities and factors determining the choice of livelihood strategies of the households in Intsika Yethu. The research findings indicated that only about 10% of the interviewed households relied solely on on-farm livelihood strategy only. Credit, remittances, market distance, affiliating to cooperatives, education and household size have a potential of influencing households to shift from on-farm livelihood strategy to other livelihood strategies. The government may need to promote programs and awareness on how households can diversify their livelihood strategies as a way of coping with economic constraints in the area.
- Full Text:
- Date Issued: 2014
- Authors: Munhenga, Daniel
- Date: 2014
- Subjects: Sustainable development -- South Africa -- Eastern Cape , Economic development projects -- South Africa -- Eastern Cape , Farm management -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc Agric (Agricultural Economics)
- Identifier: vital:11220 , http://hdl.handle.net/10353/d1019818 , Sustainable development -- South Africa -- Eastern Cape , Economic development projects -- South Africa -- Eastern Cape , Farm management -- South Africa -- Eastern Cape
- Description: Despite the continuing perceived economic centrality of agriculture in Intsika Yethu local municipality, rural households engage and pursue diverse non-farm livelihood activities to cope with diverse challenges and risks such as drought. This study assessed the importance of existing livelihood strategies adopted by the different rural households in Intsika Yethu; the link between households’ ownership and access to different ‘assets’; factors determining households’ ability to adopt certain livelihood strategies in the area. A survey of 120 households in six administrative areas and informal discussions with key informants were used to collect demographic data, data on socio-economic activities and factors determining the choice of livelihood strategies of the households in Intsika Yethu. The research findings indicated that only about 10% of the interviewed households relied solely on on-farm livelihood strategy only. Credit, remittances, market distance, affiliating to cooperatives, education and household size have a potential of influencing households to shift from on-farm livelihood strategy to other livelihood strategies. The government may need to promote programs and awareness on how households can diversify their livelihood strategies as a way of coping with economic constraints in the area.
- Full Text:
- Date Issued: 2014
The geology and metallogeny of the Otavi mountain land, Damara orogen, SWA/Namibia, with particular reference to the Berg Aukas Zn-Pb-V deposit a model of ore genesis
- Authors: Misiewicz, Julian Edward
- Date: 1988
- Subjects: Geology -- Namibia -- Damaraland , Ore deposits -- Namibia , Orogeny , Metallogeny , Geodynamics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4959 , http://hdl.handle.net/10962/d1005571 , Geology -- Namibia -- Damaraland , Ore deposits -- Namibia , Orogeny , Metallogeny , Geodynamics
- Description: The Olavi Mountain Land is a 10 000 km2 mineral province located at the eastern extremity of the exposed Northern Platform of the Damara Pan African orogenic belt. The Olavi Mountain Land is tbe most important mineral province on the Northern Platform. Exploitation of tbe Cu-Pb-Zn-V province has been on-going since the possession of the territory by the German colonial authority in 1890. Production has been mostly from four mines which in order of importance are Tsumeb, Kombat, Berg Aukas and Abeoab. A second mineral province on the Northern Platform located in the west is centred on Sesfontein where as yet only insignificant mineralization has been noted. Besides these localities, the Northern Platform is conspicuously devoid of notable mineralization. The aim of this thesis has been to document tbe Berg Aukas deposit, an important end-member type of mineralization in the Otavi Mountain Land. The basic premise bas been to show tbat the derivation and localization of the mineralization is a consequence of two broad controls which can be simply summarised as features of the basement and of the carbonate sequences. The geodynamic evolution of the Damara Belt commenced with intra-continental rifting approximately 900 Ma ago. Rift grabens trending north-east were filled by the Nosib Group which comprises mostly clastic lithologies but also some volcanics. The earliest and largest rift is referred to as the Northern Rift. Separation of the Congo, Kalahari, and proto-South American cratons resulted in rifting and rapid downwarping so that an encroaching sea and an Olavi Group carbonate shelf developed along the northern margin of the Northern Rift. Significantly, the carbonates only covered the Northern Rift in the area of the Otavi Mountain Land where a basinal dome, referred to as the Grootfontein Basement High, marked the basin edge. In the west, the carbonates covered the less important Sesfonfein Rift, and it is only in these two areas where Nosib sequences underlie the carbonate platform. Carbonate sedimentation was interrupted by a major period of crustal readjustment and the deposition of an extensive mixtite throughout the geosynclinal Swakop Trough and Northern Platform. This is referred to as the Chuos Formation and subdivides the Olavi Group into a lower Abenab and an upper Tsumeb Subgroup. Reversal of spreading led to plate collision and subduction of tbe Kalahari craton beneath the Congo craton. It was accompanied by orogenesis which resulted in F1 folding of the Northern Platform into a series of north-easterly trending intermontane basins into which a molasse sequence known as the Mulden Group was unconformably deposited. Following this major north-south deformation mild east-west compression initiated F2 folding and the formation of doubly plunging synclines. The Berg Aukas Syncline represents a primary depositional basin which was subsequently folded. The original basin was formed by late Nosib rifting wben spreading caused the Swakop geosynclinal Trough to form. Carbonates of the basal Berg Aukas Formation were deposited in a lagoonal setting typified by reef and fore-reef facies witb peri-platform conditions. Rapid subsidence caused these sediments to be overlain by deep water carbonates of the Gauss Formation. Two styles of mineralization known as the Tsumeb-type and Berg Aukas-type are stratigraphically, isotopically, and mineralogically distinct. The Tsumeb-type is a cupriferous variety of discordant bodies confined to the upper sequences beneath the Mulden unconformity. The Berg Aukas-type is a Zn-Pb variety confined to tbe basal unconformity. The Berg Aukas deposit comprises three ore bodies known as the Northern Ore Horizon, the Central Ore Body, and the Hanging Wall Ore Body. Sphalerite and galena constitute the bypogene ore. Willemite, smithsonite, cerussite, and descloizite are important supergene ores. A review of genetic models concludes that a magmatic origin initially proposed for tbe Tsumeb deposit is entirely rejected and a basin dewatering model in line with Mississippi Valley-type deposits is proposed. The syntectonic nature of mineralization at Berg Aukas and elsewhere in the Otavi Mountain Land indicates that orogenesis encouraged dewatering and leaching of metals from a broad mineralizing front along the margin of the Swakop Trough. These were transported by acidic saline brines which migrated along the clastic aquifers and structural conduits provided by the Northern Rift. Fluid inclusion studies indicate that the hydrothermal fluids at Berg Aukas were very saline (23% TDS) and were transported at temperatures ranging between 92° to 210°C. Hydrothermal fluids which mineralized Berg AukaS-type deposits migrated along the basal unconformity towards the basement high and were responsible for hydrothermally altering the basement granites and gabbros and the Nosib clastic rocks. Tsumeb-type deposits resulted by migration of fluids through the carbonate pile and along north-easterly trending basement geofractures. As a consequence of variation in transport, the Berg Aukas-type and Tsumeb-type fluids leached different sources and therefore derived mineralogically and isotopically seperable characteristics. The localization of the Berg Aukas ores was controlled by the carbonate stratigraphy and structure. Hydrothermal karsting and ore deposition took place on the contact between Massive Grey and Light Grey Dolostones which represents a permeability contrast. The movement of the hydrothermal fluids was controlled by north-south trending vertical fractures caused by F2 folding which resulted in a peric1inal structure. Hydrothermal karsting was accompanied by ca1citic, dolomitic and silicic alteration. The heated acidic fluids initiated solution collapse and a variety of breccia types. Supergene processes resulted in oxidation and upgrading of the ore. Vanadium derived indirectly from gabbros in the basement complex were transported as calcium metavanadate complexes and deposited on contact with the oxidizing base metal sulphides.
- Full Text:
- Date Issued: 1988
- Authors: Misiewicz, Julian Edward
- Date: 1988
- Subjects: Geology -- Namibia -- Damaraland , Ore deposits -- Namibia , Orogeny , Metallogeny , Geodynamics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4959 , http://hdl.handle.net/10962/d1005571 , Geology -- Namibia -- Damaraland , Ore deposits -- Namibia , Orogeny , Metallogeny , Geodynamics
- Description: The Olavi Mountain Land is a 10 000 km2 mineral province located at the eastern extremity of the exposed Northern Platform of the Damara Pan African orogenic belt. The Olavi Mountain Land is tbe most important mineral province on the Northern Platform. Exploitation of tbe Cu-Pb-Zn-V province has been on-going since the possession of the territory by the German colonial authority in 1890. Production has been mostly from four mines which in order of importance are Tsumeb, Kombat, Berg Aukas and Abeoab. A second mineral province on the Northern Platform located in the west is centred on Sesfontein where as yet only insignificant mineralization has been noted. Besides these localities, the Northern Platform is conspicuously devoid of notable mineralization. The aim of this thesis has been to document tbe Berg Aukas deposit, an important end-member type of mineralization in the Otavi Mountain Land. The basic premise bas been to show tbat the derivation and localization of the mineralization is a consequence of two broad controls which can be simply summarised as features of the basement and of the carbonate sequences. The geodynamic evolution of the Damara Belt commenced with intra-continental rifting approximately 900 Ma ago. Rift grabens trending north-east were filled by the Nosib Group which comprises mostly clastic lithologies but also some volcanics. The earliest and largest rift is referred to as the Northern Rift. Separation of the Congo, Kalahari, and proto-South American cratons resulted in rifting and rapid downwarping so that an encroaching sea and an Olavi Group carbonate shelf developed along the northern margin of the Northern Rift. Significantly, the carbonates only covered the Northern Rift in the area of the Otavi Mountain Land where a basinal dome, referred to as the Grootfontein Basement High, marked the basin edge. In the west, the carbonates covered the less important Sesfonfein Rift, and it is only in these two areas where Nosib sequences underlie the carbonate platform. Carbonate sedimentation was interrupted by a major period of crustal readjustment and the deposition of an extensive mixtite throughout the geosynclinal Swakop Trough and Northern Platform. This is referred to as the Chuos Formation and subdivides the Olavi Group into a lower Abenab and an upper Tsumeb Subgroup. Reversal of spreading led to plate collision and subduction of tbe Kalahari craton beneath the Congo craton. It was accompanied by orogenesis which resulted in F1 folding of the Northern Platform into a series of north-easterly trending intermontane basins into which a molasse sequence known as the Mulden Group was unconformably deposited. Following this major north-south deformation mild east-west compression initiated F2 folding and the formation of doubly plunging synclines. The Berg Aukas Syncline represents a primary depositional basin which was subsequently folded. The original basin was formed by late Nosib rifting wben spreading caused the Swakop geosynclinal Trough to form. Carbonates of the basal Berg Aukas Formation were deposited in a lagoonal setting typified by reef and fore-reef facies witb peri-platform conditions. Rapid subsidence caused these sediments to be overlain by deep water carbonates of the Gauss Formation. Two styles of mineralization known as the Tsumeb-type and Berg Aukas-type are stratigraphically, isotopically, and mineralogically distinct. The Tsumeb-type is a cupriferous variety of discordant bodies confined to the upper sequences beneath the Mulden unconformity. The Berg Aukas-type is a Zn-Pb variety confined to tbe basal unconformity. The Berg Aukas deposit comprises three ore bodies known as the Northern Ore Horizon, the Central Ore Body, and the Hanging Wall Ore Body. Sphalerite and galena constitute the bypogene ore. Willemite, smithsonite, cerussite, and descloizite are important supergene ores. A review of genetic models concludes that a magmatic origin initially proposed for tbe Tsumeb deposit is entirely rejected and a basin dewatering model in line with Mississippi Valley-type deposits is proposed. The syntectonic nature of mineralization at Berg Aukas and elsewhere in the Otavi Mountain Land indicates that orogenesis encouraged dewatering and leaching of metals from a broad mineralizing front along the margin of the Swakop Trough. These were transported by acidic saline brines which migrated along the clastic aquifers and structural conduits provided by the Northern Rift. Fluid inclusion studies indicate that the hydrothermal fluids at Berg Aukas were very saline (23% TDS) and were transported at temperatures ranging between 92° to 210°C. Hydrothermal fluids which mineralized Berg AukaS-type deposits migrated along the basal unconformity towards the basement high and were responsible for hydrothermally altering the basement granites and gabbros and the Nosib clastic rocks. Tsumeb-type deposits resulted by migration of fluids through the carbonate pile and along north-easterly trending basement geofractures. As a consequence of variation in transport, the Berg Aukas-type and Tsumeb-type fluids leached different sources and therefore derived mineralogically and isotopically seperable characteristics. The localization of the Berg Aukas ores was controlled by the carbonate stratigraphy and structure. Hydrothermal karsting and ore deposition took place on the contact between Massive Grey and Light Grey Dolostones which represents a permeability contrast. The movement of the hydrothermal fluids was controlled by north-south trending vertical fractures caused by F2 folding which resulted in a peric1inal structure. Hydrothermal karsting was accompanied by ca1citic, dolomitic and silicic alteration. The heated acidic fluids initiated solution collapse and a variety of breccia types. Supergene processes resulted in oxidation and upgrading of the ore. Vanadium derived indirectly from gabbros in the basement complex were transported as calcium metavanadate complexes and deposited on contact with the oxidizing base metal sulphides.
- Full Text:
- Date Issued: 1988
Freshwater invasive alien crayfish species in South Africa: testing eDNA assessment and DNA barcoding
- Mdidimba, Nonkazimulo Dorothea
- Authors: Mdidimba, Nonkazimulo Dorothea
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424413 , vital:72151
- Description: The expansion of the wild populations of the two invasive alien crayfish species, i.e., Cherax quadricarinatus and Procambarus clarkii in South Africa is of high concern. Given this, innovative and improved monitoring methods are required to be explored in order to effectively detect and manage their spread. Environmental DNA (eDNA) has shown promising and reliable results to detect and monitor alien crayfish in freshwater systems even at low densities. This research study aimed to field-test the application of eDNA for detecting and monitoring invasive alien freshwater crayfish species (IAFCs) in South African freshwater systems (Chapter 2). Further, this study also aimed to confirm the true taxonomic identity of the IAFCs in South African freshwater systems by using DNA barcoding to avoid potential misidentifications with morphological identification alone (Chapter 3). Also, ectocommensal temnocephalans and leeches attached to the crayfishes were also identified with DNA barcoding. The mitochondrial COI gene fragment of the crayfishes and the ectocommensal temnocephalans and leeches was amplified, sequenced, and used for species identification. For eDNA monitoring of C. cainii, C. quadricarinatus and P. clarkii, water samples were collected from Eastern Cape, Free State and KwaZulu Natal sites that are known to house these species. The current study did not detect the eDNA of the wild populations of both C. quadricarinatus and P. clarkii. This failure was encountered despite employing several methods, such as, end-point polymerase chain reaction (PCR), quantitative PCR (qPCR) and next-generation sequencing (NGS). The eDNA assessment to detect IAFCs in the wild populations is discussed in detail, and corrective measures suggested (Chapter 2). However, only C. cainii was able to be detected by eDNA. Cherax cainii is housed/farmed in an aquaculture facility (Vaughn Bursey’s Stock Farm in Eastern Cape) with large number of individuals per pond. For this, NGS was able to detect C. cainii but the other two methods, end-point PCR and qPCR were not able to detect the species. Based on the results, refinement of eDNA monitoring methods for the South African freshwater systems is recommended. Evaluation of different DNA collection methods, preservation, DNA extraction kits and primer design to obtain effective eDNA detection is discussed as possible sources of error. Interestingly, the newly established population of P. clarkii in Mimosa Dam in Free State was infested with alien leeches, that were confirmed by DNA barcoding to be Helobdella europaea and Helobdella octatestica. Consequently, this study reports for the first time in South Africa the presence of this alien freshwater leeches. The presence of alien leeches and P. clarkii suggests a double invasion in Mimosa Dam, P. clarkii seems to continue expanding its range in the country. However, the long-established population of P. clarkii in Driehoek Farm in Mpumalanga, which has been in the country for over 30 years did not have any leech or temnocephalan infestation. This could suggest several interesting ecological phenomena, including environmental filtering over time of the co-invaders, differential source populations, and post-introduction adaptation. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Mdidimba, Nonkazimulo Dorothea
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424413 , vital:72151
- Description: The expansion of the wild populations of the two invasive alien crayfish species, i.e., Cherax quadricarinatus and Procambarus clarkii in South Africa is of high concern. Given this, innovative and improved monitoring methods are required to be explored in order to effectively detect and manage their spread. Environmental DNA (eDNA) has shown promising and reliable results to detect and monitor alien crayfish in freshwater systems even at low densities. This research study aimed to field-test the application of eDNA for detecting and monitoring invasive alien freshwater crayfish species (IAFCs) in South African freshwater systems (Chapter 2). Further, this study also aimed to confirm the true taxonomic identity of the IAFCs in South African freshwater systems by using DNA barcoding to avoid potential misidentifications with morphological identification alone (Chapter 3). Also, ectocommensal temnocephalans and leeches attached to the crayfishes were also identified with DNA barcoding. The mitochondrial COI gene fragment of the crayfishes and the ectocommensal temnocephalans and leeches was amplified, sequenced, and used for species identification. For eDNA monitoring of C. cainii, C. quadricarinatus and P. clarkii, water samples were collected from Eastern Cape, Free State and KwaZulu Natal sites that are known to house these species. The current study did not detect the eDNA of the wild populations of both C. quadricarinatus and P. clarkii. This failure was encountered despite employing several methods, such as, end-point polymerase chain reaction (PCR), quantitative PCR (qPCR) and next-generation sequencing (NGS). The eDNA assessment to detect IAFCs in the wild populations is discussed in detail, and corrective measures suggested (Chapter 2). However, only C. cainii was able to be detected by eDNA. Cherax cainii is housed/farmed in an aquaculture facility (Vaughn Bursey’s Stock Farm in Eastern Cape) with large number of individuals per pond. For this, NGS was able to detect C. cainii but the other two methods, end-point PCR and qPCR were not able to detect the species. Based on the results, refinement of eDNA monitoring methods for the South African freshwater systems is recommended. Evaluation of different DNA collection methods, preservation, DNA extraction kits and primer design to obtain effective eDNA detection is discussed as possible sources of error. Interestingly, the newly established population of P. clarkii in Mimosa Dam in Free State was infested with alien leeches, that were confirmed by DNA barcoding to be Helobdella europaea and Helobdella octatestica. Consequently, this study reports for the first time in South Africa the presence of this alien freshwater leeches. The presence of alien leeches and P. clarkii suggests a double invasion in Mimosa Dam, P. clarkii seems to continue expanding its range in the country. However, the long-established population of P. clarkii in Driehoek Farm in Mpumalanga, which has been in the country for over 30 years did not have any leech or temnocephalan infestation. This could suggest several interesting ecological phenomena, including environmental filtering over time of the co-invaders, differential source populations, and post-introduction adaptation. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2023
- Full Text:
- Date Issued: 2023-10-13
Assessing MODIS evapotranspiration data for hydrological modelling in South Africa
- Mazibuko, Sbongiseni Christian
- Authors: Mazibuko, Sbongiseni Christian
- Date: 2017
- Subjects: Evapotranspiration , Evapotranspiration -- Measurement , Hydrologic models , Hydrologic models -- South Africa , MODIS (Spectroradiometer)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/8009 , vital:21334
- Description: Evapotranspiration as a major component of the water balance has been identified as a key factor in hydrological modelling. Water management can be improved by means of increased use of reliable methods for estimating evapotranspiration. The limited availability of measured climate and discharge data sets, particularly in the developing world, restricts the reliability of hydrological models in these regions. Furthermore, rapid changes in hydrological systems with increasing development mean uncertainties in water resource estimation are growing. These changes are related to the modification of catchment hydrological processes with increasing human activity. Dealing with data uncertainty and quantifying the impacts of catchment activities are significant challenges that scientists in the field of hydrology face today. Uncertainties in hydrometeorological data are associated with poor observation networks that provide data at point scales which are not adequately representative of the inherent heterogeneity within catchment processes. Using uncertain data in model applications reduces the predictive power of hydrological models as well as the ability to validate the model outcomes. This study examines the potential of using remote sensing-based evapotranspiration data to reduce uncertainty in the climatic forcing data and constraining the output of a rainfall-runoff hydrological model. It is common to use fixed seasonally variable potential evapotranspiration (PET) instead of temporally varying PET data as inputs to standard rainfall-runoff models. Part of the reason is that there are relatively few stations available to measure a variety of meteorological input data needed to compute PET, as well as the apparent lack of sensitivity of rainfall-runoff models to different types of PET inputs. As hydrometeorological data become more readily available through the use of earth observation systems, it is important to determine whether rainfall-runoff models are sensitive to time-varying PET derived from these earth observations systems. Further potential includes the use of actual evapotranspiration (ETa) from this type of data to constrain model outputs and improve model realism. It is assumed that a better representation of evapotranspiration demands could improve the efficiency of models, and this study explores some of these issues. The study used evapotranspiration estimates (PET and ETa) from the MOD16 global product with one of the most widely used hydrological models in South Africa. The investigation included applying the Pitman model in a number of case study catchments located in different climatic regions of the country. The main objectives of the study included (i) the establishment of behavioural model parameter sets that generate acceptable hydrological response under both naturalised and present-day conditions, (ii) the use of time-varying PET estimates derived from MOD16 data to force the model, and (iii) the use of MOD16 ETa estimates to constrain model-simulated ETa. Before examining the use of different PET forcing data in the model, a two-step modelling approached was employed both a single-run and an uncertainty version of the Pitman model. During the first step (using a single-run version), available information on catchment physical properties and regionalised groundwater recharge together with model calibration principles were used to develop model functionality understanding and establish initial parameter sets. The outcomes from the first step were used to define uncertain parameter ranges for the use in the uncertainty version of the Pitman model (second step). Further, catchment water uses were quantified to ensure comparability with present-day flow conditions represented by the stream flow records. The effects of forcing the Pitman model with MOD16-based time-varying PET data inputs were evaluated using static and dynamic sensitivity analysis approaches. In the static approach, parameter sets calibrated using fixed seasonal distributions of PET data remain unchanged when forcing the model with other forms of PET, whereas in the dynamic method, the model is recalibrated with changing PET inputs. In both approaches, model sensitivity was assessed by comparing objective function statistics of reference flow simulations with those simulations incorporating changing PET data inputs. The use of the MOD16 ETa data to constrain model- simulated evapotranspiration losses was conducted by calibrating the parameters such that the simulated-ETa matched the evapotranspiration loss estimated from the MOD16 data. Despite issues around model equifinality and significant uncertainty within water use information, the Pitman model simulations were generally satisfactory and compared with observed stream flow data where available. The use of time-varying PET data does not improve the efficiency of the model when both static and dynamic sensitivity approaches are used. This was highly expected with the static approach where fixed model parameter sets do not account for the changes in evapotranspiration demands. However, with the dynamic approach, it was difficult to conclude why the model efficiency did not improve given the flexibility of the model to achieve appropriate parameter sets to different forms of PET. The study noted that the insensitivity of the model to changes in PET demands could be due to uncertainties in the model structure and MOD16 data. Attempts to constrain the model-simulated actual evapotranspiration with MOD16 ETa estimates were hampered by large errors in the MOD16 data and resulted in the non-closure of the catchment annual water balance, even when likely errors in the other components of the water balance were accounted for. There is still a great deal of work that needs to be done to reduce uncertainties associated with the use of earth observation data in hydrological modelling. This study has identified some of the specific gaps within the application of evapotranspiration data from earth observation information. While the MOD16 data applied with the Pitman model did not achieve improved simulations, the study has demonstrated the enormous potential of the data product in the future should the identified uncertainties be resolved. Lastly, the investigation highlighted some of the possible model structural uncertainties specifically associated with the simplified soil-moisture accounting routines within the model. It is possible that amending the model structure through investigating the dynamics of the relationship between soil moisture and evapotranspiration losses would assist in the improved utilisation of earth observation products related to the MOD16 ET data.
- Full Text:
- Date Issued: 2017
- Authors: Mazibuko, Sbongiseni Christian
- Date: 2017
- Subjects: Evapotranspiration , Evapotranspiration -- Measurement , Hydrologic models , Hydrologic models -- South Africa , MODIS (Spectroradiometer)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/8009 , vital:21334
- Description: Evapotranspiration as a major component of the water balance has been identified as a key factor in hydrological modelling. Water management can be improved by means of increased use of reliable methods for estimating evapotranspiration. The limited availability of measured climate and discharge data sets, particularly in the developing world, restricts the reliability of hydrological models in these regions. Furthermore, rapid changes in hydrological systems with increasing development mean uncertainties in water resource estimation are growing. These changes are related to the modification of catchment hydrological processes with increasing human activity. Dealing with data uncertainty and quantifying the impacts of catchment activities are significant challenges that scientists in the field of hydrology face today. Uncertainties in hydrometeorological data are associated with poor observation networks that provide data at point scales which are not adequately representative of the inherent heterogeneity within catchment processes. Using uncertain data in model applications reduces the predictive power of hydrological models as well as the ability to validate the model outcomes. This study examines the potential of using remote sensing-based evapotranspiration data to reduce uncertainty in the climatic forcing data and constraining the output of a rainfall-runoff hydrological model. It is common to use fixed seasonally variable potential evapotranspiration (PET) instead of temporally varying PET data as inputs to standard rainfall-runoff models. Part of the reason is that there are relatively few stations available to measure a variety of meteorological input data needed to compute PET, as well as the apparent lack of sensitivity of rainfall-runoff models to different types of PET inputs. As hydrometeorological data become more readily available through the use of earth observation systems, it is important to determine whether rainfall-runoff models are sensitive to time-varying PET derived from these earth observations systems. Further potential includes the use of actual evapotranspiration (ETa) from this type of data to constrain model outputs and improve model realism. It is assumed that a better representation of evapotranspiration demands could improve the efficiency of models, and this study explores some of these issues. The study used evapotranspiration estimates (PET and ETa) from the MOD16 global product with one of the most widely used hydrological models in South Africa. The investigation included applying the Pitman model in a number of case study catchments located in different climatic regions of the country. The main objectives of the study included (i) the establishment of behavioural model parameter sets that generate acceptable hydrological response under both naturalised and present-day conditions, (ii) the use of time-varying PET estimates derived from MOD16 data to force the model, and (iii) the use of MOD16 ETa estimates to constrain model-simulated ETa. Before examining the use of different PET forcing data in the model, a two-step modelling approached was employed both a single-run and an uncertainty version of the Pitman model. During the first step (using a single-run version), available information on catchment physical properties and regionalised groundwater recharge together with model calibration principles were used to develop model functionality understanding and establish initial parameter sets. The outcomes from the first step were used to define uncertain parameter ranges for the use in the uncertainty version of the Pitman model (second step). Further, catchment water uses were quantified to ensure comparability with present-day flow conditions represented by the stream flow records. The effects of forcing the Pitman model with MOD16-based time-varying PET data inputs were evaluated using static and dynamic sensitivity analysis approaches. In the static approach, parameter sets calibrated using fixed seasonal distributions of PET data remain unchanged when forcing the model with other forms of PET, whereas in the dynamic method, the model is recalibrated with changing PET inputs. In both approaches, model sensitivity was assessed by comparing objective function statistics of reference flow simulations with those simulations incorporating changing PET data inputs. The use of the MOD16 ETa data to constrain model- simulated evapotranspiration losses was conducted by calibrating the parameters such that the simulated-ETa matched the evapotranspiration loss estimated from the MOD16 data. Despite issues around model equifinality and significant uncertainty within water use information, the Pitman model simulations were generally satisfactory and compared with observed stream flow data where available. The use of time-varying PET data does not improve the efficiency of the model when both static and dynamic sensitivity approaches are used. This was highly expected with the static approach where fixed model parameter sets do not account for the changes in evapotranspiration demands. However, with the dynamic approach, it was difficult to conclude why the model efficiency did not improve given the flexibility of the model to achieve appropriate parameter sets to different forms of PET. The study noted that the insensitivity of the model to changes in PET demands could be due to uncertainties in the model structure and MOD16 data. Attempts to constrain the model-simulated actual evapotranspiration with MOD16 ETa estimates were hampered by large errors in the MOD16 data and resulted in the non-closure of the catchment annual water balance, even when likely errors in the other components of the water balance were accounted for. There is still a great deal of work that needs to be done to reduce uncertainties associated with the use of earth observation data in hydrological modelling. This study has identified some of the specific gaps within the application of evapotranspiration data from earth observation information. While the MOD16 data applied with the Pitman model did not achieve improved simulations, the study has demonstrated the enormous potential of the data product in the future should the identified uncertainties be resolved. Lastly, the investigation highlighted some of the possible model structural uncertainties specifically associated with the simplified soil-moisture accounting routines within the model. It is possible that amending the model structure through investigating the dynamics of the relationship between soil moisture and evapotranspiration losses would assist in the improved utilisation of earth observation products related to the MOD16 ET data.
- Full Text:
- Date Issued: 2017
Ecological effects of impoundments in the Buffalo River, Eastern Cape, with particular reference to the distribution of blackflies (Diptera : simuliidae)
- Authors: Palmer, Robert William
- Date: 1992
- Subjects: Stream ecology -- South Africa -- Buffalo River (Eastern Cape) Dipter -- South Africa -- Buffalo River (Eastern Cape)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6028 , http://hdl.handle.net/10962/d1006157
- Description: This thesis examines the extent and intensity of the effects of impoundments on selected physical, chemical and biotic conditions in an impounded southern African river. Life-history characteristics and environmental requirements which determine the success of impoundment-outlet blackflies in southern Africa were studied. Difficulties with the identification of immature blackflies led to a search for additional diagnostic characters, the description of larvae of seven species previously unknown, and the development of new keys to the species of Simulium (larvae and pupae) in southern Africa. Distribution records for each species are presented, and their ecology is summarised. Three pairs of closely related species, which were formerly indistinguishable, can now be recognised by differences between the structure of their cephalic fan microtrichia. Monthly physical, chemical and invertebrate samples at 16 sites upstream and downstream of four impoundments in the Buffalo River, eastern Cape, were taken over a period of two years. The downstream effects of impoundments on these parameters depended on the variable examined, the position of the impoundment along the river profile, the depth from which water was released, and the quality of the inflowing water. Impoundments in the Buffalo River caused an upstream shift of the thermal and suspended organic conditions, and the distribution of blackfly species. Surface-release impoundments in the clean, upper-reaches of the river caused increases in water temperature (by as much as 8ºC) and chlorophyll a (by as much as 600%). Recovery to riverine conditions was within 2.6 to 18.4 km, depending on flow. A polluted, surface-release impoundment in the middle-reaches of the river had a slight dampening effect on river temperatures, converted the particle size spectrum of the river from small (<80 μm) to large (250-1000 μm), and improved the water quality of the downstream reaches (with the exception of nitrate concentrations, which were higher in the tailwaters compared to inflowing water). An impoundment in the lower reaches caused reductions in maximum temperature of up to 6ºC when releasing water from the surface, and up to 16ºC when releasing water from the bottom. Bottom-released water carried high concentrations (36 to 190 g m³) of small (<5 μm) and largely inorganic (86 to 93%) material.Twenty species of blackflies were found in the Buffalo River, of which 18 were distinguishable as larvae. They were divided into those which were widespread (5 taxa), those restricted to waterfalls and mountain torrents (2 taxa), those found in the foothill stony run zone (6 taxa), and rare taxa (5 taxa). Impoundments in the Buffalo River did not alter population densities of blackfly larvae, but did alter blackfly species composition, favouring five species commonly found in mid-order streams in southern Africa (s. meduseaforme, S. hargreavesi, S. nigritarse, S. adersi and s. damnosum s.l.) at the expense of upper-reach species (s. rutherfoordi, S. letabum and s. impukane). These five species are regarded as typical of impoundment-outlets, and were small, multivoltine flies whose larvae shared a generalised cephalic fan microtrichial structure, consisting of a single row of moderately differentiated microtrichia. A strong relation was found between cephalic fan microtrichial structure and larval habitats: Taxa found in fast-flowing, clear water had a more complex fan structure compared to those found in slow-flowing, turbid water. It is concluded that impoundment-induced changes to hydrodynamics and transported material (food) are important factors which have changed the distribution of blackflies in southern Africa in recent times. These changes are more severe downstream of upper-reach impoundments than middle or lower-reach impoundments.
- Full Text:
- Date Issued: 1992
- Authors: Palmer, Robert William
- Date: 1992
- Subjects: Stream ecology -- South Africa -- Buffalo River (Eastern Cape) Dipter -- South Africa -- Buffalo River (Eastern Cape)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6028 , http://hdl.handle.net/10962/d1006157
- Description: This thesis examines the extent and intensity of the effects of impoundments on selected physical, chemical and biotic conditions in an impounded southern African river. Life-history characteristics and environmental requirements which determine the success of impoundment-outlet blackflies in southern Africa were studied. Difficulties with the identification of immature blackflies led to a search for additional diagnostic characters, the description of larvae of seven species previously unknown, and the development of new keys to the species of Simulium (larvae and pupae) in southern Africa. Distribution records for each species are presented, and their ecology is summarised. Three pairs of closely related species, which were formerly indistinguishable, can now be recognised by differences between the structure of their cephalic fan microtrichia. Monthly physical, chemical and invertebrate samples at 16 sites upstream and downstream of four impoundments in the Buffalo River, eastern Cape, were taken over a period of two years. The downstream effects of impoundments on these parameters depended on the variable examined, the position of the impoundment along the river profile, the depth from which water was released, and the quality of the inflowing water. Impoundments in the Buffalo River caused an upstream shift of the thermal and suspended organic conditions, and the distribution of blackfly species. Surface-release impoundments in the clean, upper-reaches of the river caused increases in water temperature (by as much as 8ºC) and chlorophyll a (by as much as 600%). Recovery to riverine conditions was within 2.6 to 18.4 km, depending on flow. A polluted, surface-release impoundment in the middle-reaches of the river had a slight dampening effect on river temperatures, converted the particle size spectrum of the river from small (<80 μm) to large (250-1000 μm), and improved the water quality of the downstream reaches (with the exception of nitrate concentrations, which were higher in the tailwaters compared to inflowing water). An impoundment in the lower reaches caused reductions in maximum temperature of up to 6ºC when releasing water from the surface, and up to 16ºC when releasing water from the bottom. Bottom-released water carried high concentrations (36 to 190 g m³) of small (<5 μm) and largely inorganic (86 to 93%) material.Twenty species of blackflies were found in the Buffalo River, of which 18 were distinguishable as larvae. They were divided into those which were widespread (5 taxa), those restricted to waterfalls and mountain torrents (2 taxa), those found in the foothill stony run zone (6 taxa), and rare taxa (5 taxa). Impoundments in the Buffalo River did not alter population densities of blackfly larvae, but did alter blackfly species composition, favouring five species commonly found in mid-order streams in southern Africa (s. meduseaforme, S. hargreavesi, S. nigritarse, S. adersi and s. damnosum s.l.) at the expense of upper-reach species (s. rutherfoordi, S. letabum and s. impukane). These five species are regarded as typical of impoundment-outlets, and were small, multivoltine flies whose larvae shared a generalised cephalic fan microtrichial structure, consisting of a single row of moderately differentiated microtrichia. A strong relation was found between cephalic fan microtrichial structure and larval habitats: Taxa found in fast-flowing, clear water had a more complex fan structure compared to those found in slow-flowing, turbid water. It is concluded that impoundment-induced changes to hydrodynamics and transported material (food) are important factors which have changed the distribution of blackflies in southern Africa in recent times. These changes are more severe downstream of upper-reach impoundments than middle or lower-reach impoundments.
- Full Text:
- Date Issued: 1992
The demography, breeding biology and management of two mullet species (Pisces : Mugilidae) in the Eastern Cape, South Africa
- Authors: Bok, Anton
- Date: 1984
- Subjects: Fishes -- South Africa -- Eastern Cape Mullidae -- South Africa -- Eastern Cape Estuarine ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5213 , http://hdl.handle.net/10962/d1004931
- Description: Aspects of the life history of Myxus capensis which were likely to be most affected by man-induced habitat changes, were studied in the eastern Cape. Myxus capensis was found to be specialized for a catadromous life history. The fry migrate into freshwater reaches of rivers within a few months of being spawned at sea and return to an estuarine or marine environment when maximum size has been attained and large energy reserves necessary for spawning have been accumulated. Myxus capensis penetrates considerable distances up eastern Cape rivers and although present in the upper reaches of some estuaries, is only common in freshwater-dominated systems. Myxus capensis has adapted its life history style in a number of ways to overcome the constraints associated with the spatial separation of the freshwater feeding areas and the marine spawning grounds in a region prone to droughts and erratic river flow. Research on the more estuarine-dependent Mugil cephalus, which is also found in the freshwater reaches of eastern Cape rivers, enabled useful comparisons to be drawn. As the latter species is not dependent on a freshwater phase in its life cycle, it is subject to different selection pressures. This comparative approach gave insights into the adaptive significance of the life history tactics of Myxus capensis. Myxus capensis displays a number of life history tactics characteristic of migratory fish species which are thought to increase population fecundity by increasing the number of large females and hence maximizing egg production. These include a sex ratio in favour of females, faster female growth, females remaining longer in the freshwater feeding areas and reaching a larger ultimate size. Possible adaptations to the periodic isolation of the feeding and spawning areas include: (i) the development of ripe gonads only in estuarine or marine areas when access to the spawning grounds is ensured; (ii) year-round spawning and hence recruitment which enables the erratic floods to be used at any time for downriver spawning migrations and reduces the chances of total recruitment failure due to short-term adverse environmental conditions and (iii) a relatively wide range of size and age at first (and final) sexual maturity (2+ to 5+ years); this tends to ensure successful reproduction and recruitment in spite of a series of poor years, as well as dampen population fluctuations after long periods of isolation in fresh water. The dependence of Myxus capensis on the freshwater reaches of eastern Cape rivers makes this species vulnerable to man-induced habitat changes. The erection of barriers to migration has cut off large stretches of suitable habitat and almost completely eliminated Myxus capensis from certain rivers. This detrimental effect has been largely responsible for the recent inclusion of this species on the Red Data list of endangered fish species in South Africa. This study demonstrated the considerable fisheries potential of both mullet species and this should ensure that their conservation and wise utilization be given high priority. Management proposals include: (i) the netting and lifting of Myxus capensis over barriers to migration; (ii) the construction of fish ladders when feasible and (iii) the artificial propagation of this species to enable large-scale stockings of existing man-made impoundments as well as natural habitats to be carried out. It is predicted that the life history characteristics of Myxus capensis, which evolved in response to an erratic freshwater environment, should ensure that when man-induced habitat changes are rectified, this species will again flourish in eastern Cape rivers.
- Full Text:
- Date Issued: 1984
- Authors: Bok, Anton
- Date: 1984
- Subjects: Fishes -- South Africa -- Eastern Cape Mullidae -- South Africa -- Eastern Cape Estuarine ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5213 , http://hdl.handle.net/10962/d1004931
- Description: Aspects of the life history of Myxus capensis which were likely to be most affected by man-induced habitat changes, were studied in the eastern Cape. Myxus capensis was found to be specialized for a catadromous life history. The fry migrate into freshwater reaches of rivers within a few months of being spawned at sea and return to an estuarine or marine environment when maximum size has been attained and large energy reserves necessary for spawning have been accumulated. Myxus capensis penetrates considerable distances up eastern Cape rivers and although present in the upper reaches of some estuaries, is only common in freshwater-dominated systems. Myxus capensis has adapted its life history style in a number of ways to overcome the constraints associated with the spatial separation of the freshwater feeding areas and the marine spawning grounds in a region prone to droughts and erratic river flow. Research on the more estuarine-dependent Mugil cephalus, which is also found in the freshwater reaches of eastern Cape rivers, enabled useful comparisons to be drawn. As the latter species is not dependent on a freshwater phase in its life cycle, it is subject to different selection pressures. This comparative approach gave insights into the adaptive significance of the life history tactics of Myxus capensis. Myxus capensis displays a number of life history tactics characteristic of migratory fish species which are thought to increase population fecundity by increasing the number of large females and hence maximizing egg production. These include a sex ratio in favour of females, faster female growth, females remaining longer in the freshwater feeding areas and reaching a larger ultimate size. Possible adaptations to the periodic isolation of the feeding and spawning areas include: (i) the development of ripe gonads only in estuarine or marine areas when access to the spawning grounds is ensured; (ii) year-round spawning and hence recruitment which enables the erratic floods to be used at any time for downriver spawning migrations and reduces the chances of total recruitment failure due to short-term adverse environmental conditions and (iii) a relatively wide range of size and age at first (and final) sexual maturity (2+ to 5+ years); this tends to ensure successful reproduction and recruitment in spite of a series of poor years, as well as dampen population fluctuations after long periods of isolation in fresh water. The dependence of Myxus capensis on the freshwater reaches of eastern Cape rivers makes this species vulnerable to man-induced habitat changes. The erection of barriers to migration has cut off large stretches of suitable habitat and almost completely eliminated Myxus capensis from certain rivers. This detrimental effect has been largely responsible for the recent inclusion of this species on the Red Data list of endangered fish species in South Africa. This study demonstrated the considerable fisheries potential of both mullet species and this should ensure that their conservation and wise utilization be given high priority. Management proposals include: (i) the netting and lifting of Myxus capensis over barriers to migration; (ii) the construction of fish ladders when feasible and (iii) the artificial propagation of this species to enable large-scale stockings of existing man-made impoundments as well as natural habitats to be carried out. It is predicted that the life history characteristics of Myxus capensis, which evolved in response to an erratic freshwater environment, should ensure that when man-induced habitat changes are rectified, this species will again flourish in eastern Cape rivers.
- Full Text:
- Date Issued: 1984
Comparative biogeography and ecology of freshwater fishes in the Breede and associated river systems, South Africa
- Authors: Chakona, Albert
- Date: 2012
- Subjects: Freshwater fishes -- South Africa -- Breede River , Freshwater fishes -- South Africa -- Geographical distribution , Freshwater fishes -- Ecology , Feshwater fishes -- Genetics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5372 , http://hdl.handle.net/10962/d1015694
- Description: Distribution patterns and levels of genetic diversity in extant taxa are a product of complex palaeogeographic processes and climatic oscillations as well as the species’ intrinsic ecological adaptations. The Cape Floristic Region of South Africa presents a unique system for studying the processes that promote species diversification and distribution patterns. This region has a high degree of endemism of both terrestrial and aquatic biota and is clearly isolated from neighbouring areas by the Cape Fold Mountains and the Great Escarpment. The objective of this study was to firstly examine the ecology of freshwater fishes belonging to the genera Galaxias, Pseudobarbus and Sandelia in the south-western CFR. This was followed by an assessment of the genetic diversity of these taxa. Unique lineages were identified and their distribution was mapped. The work aimed to explore the role of the region’s complex palaeogeographic and climatic history as well as the role of the species’ ecological adaptations in driving lineage diversification and shaping contemporary distribution patterns. The four main components of the study can be summarised as follows: 1. Habitat associations of three widely distributed lineages of Galaxias zebratus Pseudobarbus burchelli and Sandelia capensis were evaluated at multiple localities in minimally disturbed mountain tributaries of the Breede, Duiwenhoks and Goukou River systems. The lineages have distinct habitat associations which were related to differences in their morphological traits. The slender-bodied Galaxias ‘nebula’ and the fusiform-shaped Pseudobarbus ‘Breede’ are capable of exploiting upper reaches with faster water velocity. By contrast, the laterally compressed Sandelia ‘eastern’ is restricted to lower reaches, making this lineage more susceptible to a wide array of impacts. 2. A recently discovered lineage of Galaxias zebratus, (Galaxias ‘nebula’), was found to be capable of tolerating emersion for a prolonged period of time. This is the first time that such capabilities have been documented in an African galaxiid. These adaptations have implications for the interpretation of Galaxias ‘nebula’s wide distribution range. 3. The phylogeography of Galaxias ‘nebula’ across its entire distribution range was investigated using two mitochondrial genes (cytochrome c oxidase subunit I (COI) and cytochrome b (cyt b)). This lineage has a complex evolutionary history that was influenced by both intrinsic and extrinsic factors. Rare events such as episodic drainage connections during Pleistocene and Holocene pluvial periods, possibly augmented by river confluences during periods of lower sea-levels and river capture events seem to be the most credible explanation for the extensive contemporary distribution and the relatively shallow genetic divergence between different river systems. 4. Mitochondrial cyt b sequences were used (i) to assess genetic diversity in G. zebratus, P. burchelli and S. capensis from the south-western CFR and (ii) to determine the roles of intrinsic ecological adaptations and extrinsic landscape and climatic changes in promoting genetic diversification and shaping present day distribution patterns of lineages in the three taxa. Marine incursions during periods of major sea-level transgressions are proposed to have isolated populations in upland refugia, thereby driving allopatric divergence in these species. Subsequent connections of rivers during wetter periods and lower sea-levels are proposed to have facilitated post-speciation dispersal of lineages to attain present day distribution patterns. While detailed morphological studies and further genetic analysis are needed to substantiate the taxonomic status of the newly discovered lineages of Galaxias zebratus, Pseudobarbus burchelli and Sandelia capensis, results of the present study indicate that the south-western CFR represents a previously unrecognised centre of freshwater fish diversity and microendemism in the broader Cape Floristic Region. Accurate identification of lineages and comprehensive mapping of their distribution is a fundamental pre-requisite for ecological studies, assessing conservation status and implementation of appropriate conservation measures.
- Full Text:
- Date Issued: 2012
- Authors: Chakona, Albert
- Date: 2012
- Subjects: Freshwater fishes -- South Africa -- Breede River , Freshwater fishes -- South Africa -- Geographical distribution , Freshwater fishes -- Ecology , Feshwater fishes -- Genetics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5372 , http://hdl.handle.net/10962/d1015694
- Description: Distribution patterns and levels of genetic diversity in extant taxa are a product of complex palaeogeographic processes and climatic oscillations as well as the species’ intrinsic ecological adaptations. The Cape Floristic Region of South Africa presents a unique system for studying the processes that promote species diversification and distribution patterns. This region has a high degree of endemism of both terrestrial and aquatic biota and is clearly isolated from neighbouring areas by the Cape Fold Mountains and the Great Escarpment. The objective of this study was to firstly examine the ecology of freshwater fishes belonging to the genera Galaxias, Pseudobarbus and Sandelia in the south-western CFR. This was followed by an assessment of the genetic diversity of these taxa. Unique lineages were identified and their distribution was mapped. The work aimed to explore the role of the region’s complex palaeogeographic and climatic history as well as the role of the species’ ecological adaptations in driving lineage diversification and shaping contemporary distribution patterns. The four main components of the study can be summarised as follows: 1. Habitat associations of three widely distributed lineages of Galaxias zebratus Pseudobarbus burchelli and Sandelia capensis were evaluated at multiple localities in minimally disturbed mountain tributaries of the Breede, Duiwenhoks and Goukou River systems. The lineages have distinct habitat associations which were related to differences in their morphological traits. The slender-bodied Galaxias ‘nebula’ and the fusiform-shaped Pseudobarbus ‘Breede’ are capable of exploiting upper reaches with faster water velocity. By contrast, the laterally compressed Sandelia ‘eastern’ is restricted to lower reaches, making this lineage more susceptible to a wide array of impacts. 2. A recently discovered lineage of Galaxias zebratus, (Galaxias ‘nebula’), was found to be capable of tolerating emersion for a prolonged period of time. This is the first time that such capabilities have been documented in an African galaxiid. These adaptations have implications for the interpretation of Galaxias ‘nebula’s wide distribution range. 3. The phylogeography of Galaxias ‘nebula’ across its entire distribution range was investigated using two mitochondrial genes (cytochrome c oxidase subunit I (COI) and cytochrome b (cyt b)). This lineage has a complex evolutionary history that was influenced by both intrinsic and extrinsic factors. Rare events such as episodic drainage connections during Pleistocene and Holocene pluvial periods, possibly augmented by river confluences during periods of lower sea-levels and river capture events seem to be the most credible explanation for the extensive contemporary distribution and the relatively shallow genetic divergence between different river systems. 4. Mitochondrial cyt b sequences were used (i) to assess genetic diversity in G. zebratus, P. burchelli and S. capensis from the south-western CFR and (ii) to determine the roles of intrinsic ecological adaptations and extrinsic landscape and climatic changes in promoting genetic diversification and shaping present day distribution patterns of lineages in the three taxa. Marine incursions during periods of major sea-level transgressions are proposed to have isolated populations in upland refugia, thereby driving allopatric divergence in these species. Subsequent connections of rivers during wetter periods and lower sea-levels are proposed to have facilitated post-speciation dispersal of lineages to attain present day distribution patterns. While detailed morphological studies and further genetic analysis are needed to substantiate the taxonomic status of the newly discovered lineages of Galaxias zebratus, Pseudobarbus burchelli and Sandelia capensis, results of the present study indicate that the south-western CFR represents a previously unrecognised centre of freshwater fish diversity and microendemism in the broader Cape Floristic Region. Accurate identification of lineages and comprehensive mapping of their distribution is a fundamental pre-requisite for ecological studies, assessing conservation status and implementation of appropriate conservation measures.
- Full Text:
- Date Issued: 2012
The impact of post-apartheid agricultural changes on citrus farmers in the Peddie area
- Authors: Peter, Bantu Desmond
- Date: 2017
- Subjects: Agriculture and state -- South Africa -- Eastern Cape Agriculture -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSoc
- Identifier: http://hdl.handle.net/10353/5380 , vital:29225
- Description: This study explores the impact of post-apartheid agricultural changes on citrus farmers in the Peddie area. The case study focused on the Craighead Citrus Farm at Kwatho as well as the Naudeshoek Citrus Farm, Ripplemead Citrus Farm and Siyamila Citrus Farm in the Balteni area. The study considered the effect of agricultural changes on citrus production, productivity of the farms in question, as well as the impact on poverty alleviation in Peddie District. In the study, the challenges encountered by both farmers and communities due to the agricultural changes in the new democratic dispensation were also considered. The study further considered the role played by the Department of Agriculture and Ngqushwa Local Municipality in assisting these farmers to increase citrus production in order to create employment opportunities. To achieve these objectives, a review of literature and collection of evidence in the form of interviews, and observations were conducted in the research areas. The research findings indicated that the Craighead Citrus Farms is state owned land, which belonged to Ulimocor, a parastatal under the former homeland government (Ciskei). This farm is no longer operational and is abandoned. During the period of this study the Naudeshoek Citrus Farm, Ripplemead Citrus Farm and Siyamila Citrus Farm were operational and progressing. Citrus farming in this area has potential to boost the economy, which would only be possible with the establishment of partnerships between the emerging farmers, government, commercial farmers and Ngqushwa Local Municipality.
- Full Text:
- Date Issued: 2017
- Authors: Peter, Bantu Desmond
- Date: 2017
- Subjects: Agriculture and state -- South Africa -- Eastern Cape Agriculture -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSoc
- Identifier: http://hdl.handle.net/10353/5380 , vital:29225
- Description: This study explores the impact of post-apartheid agricultural changes on citrus farmers in the Peddie area. The case study focused on the Craighead Citrus Farm at Kwatho as well as the Naudeshoek Citrus Farm, Ripplemead Citrus Farm and Siyamila Citrus Farm in the Balteni area. The study considered the effect of agricultural changes on citrus production, productivity of the farms in question, as well as the impact on poverty alleviation in Peddie District. In the study, the challenges encountered by both farmers and communities due to the agricultural changes in the new democratic dispensation were also considered. The study further considered the role played by the Department of Agriculture and Ngqushwa Local Municipality in assisting these farmers to increase citrus production in order to create employment opportunities. To achieve these objectives, a review of literature and collection of evidence in the form of interviews, and observations were conducted in the research areas. The research findings indicated that the Craighead Citrus Farms is state owned land, which belonged to Ulimocor, a parastatal under the former homeland government (Ciskei). This farm is no longer operational and is abandoned. During the period of this study the Naudeshoek Citrus Farm, Ripplemead Citrus Farm and Siyamila Citrus Farm were operational and progressing. Citrus farming in this area has potential to boost the economy, which would only be possible with the establishment of partnerships between the emerging farmers, government, commercial farmers and Ngqushwa Local Municipality.
- Full Text:
- Date Issued: 2017
South African farm wages and working conditions: with special reference to the Albany district, 1957 to 1977
- Authors: Antrobus, Geoffrey Gordon
- Date: 1984
- Subjects: Agricultural wages -- South Africa -- Eastern Cape , Agricultural laborers -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1028 , http://hdl.handle.net/10962/d1003722
- Description: The focus of the study is the wages and working conditions of farm labourers in commercial agriculture. After an outline examination of the broad trends in employment and wages in the agricultural industry as a whole, the emphasis falls on a micro-study of employment practices in the Eastern Cape magisterial district of Albany. The results of a survey of farmers was used to determine the level of wages, including payments in kind, the value of housing, cropping and grazing rights. It was found that cash wages made up only 25% of the total remuneration of R684 per annum, while purchased and farm produced rations made up a further 40% of the total. A survey conducted in the Albany district two decades previously was used to compare the real earnings in 1957 and 1977. Although real cash wages and rations increased over the twenty year period the restriction of cropping and grazing rights had the effect of keeping real earnings static. In the light of the improvement of other working conditions, such as the reduction in working hours, however, it is concluded that some increase in real wages did occur . It is evident that there are no clear-cut recipes for successful farm labour management and no unequivocal statements should be made about the most visible element, namely cash wages.
- Full Text:
- Date Issued: 1984
- Authors: Antrobus, Geoffrey Gordon
- Date: 1984
- Subjects: Agricultural wages -- South Africa -- Eastern Cape , Agricultural laborers -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1028 , http://hdl.handle.net/10962/d1003722
- Description: The focus of the study is the wages and working conditions of farm labourers in commercial agriculture. After an outline examination of the broad trends in employment and wages in the agricultural industry as a whole, the emphasis falls on a micro-study of employment practices in the Eastern Cape magisterial district of Albany. The results of a survey of farmers was used to determine the level of wages, including payments in kind, the value of housing, cropping and grazing rights. It was found that cash wages made up only 25% of the total remuneration of R684 per annum, while purchased and farm produced rations made up a further 40% of the total. A survey conducted in the Albany district two decades previously was used to compare the real earnings in 1957 and 1977. Although real cash wages and rations increased over the twenty year period the restriction of cropping and grazing rights had the effect of keeping real earnings static. In the light of the improvement of other working conditions, such as the reduction in working hours, however, it is concluded that some increase in real wages did occur . It is evident that there are no clear-cut recipes for successful farm labour management and no unequivocal statements should be made about the most visible element, namely cash wages.
- Full Text:
- Date Issued: 1984
Ecological consequences of non-native fish invasion in Eastern Cape headwater streams
- Authors: Ellender, Bruce Robert
- Date: 2014
- Subjects: Fishery management -- South Africa -- Eastern Cape Fishes -- Conservation -- South Africa Introduced fishes -- South Africa -- Eastern Cape Introduced organisms
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/69065 , vital:29380
- Description: The introduction, spread and concomitant impacts of non-native species are a global problem. Fish are among the most widely introduced vertebrate groups, with their impacts affecting multiple levels of organisation- from individuals, populations and communities, to entire ecosystems. In South Africa, the largest perceived threat to range-restricted endemic headwater stream fishes is said to be invasion by non-native fishes, however, as is the case elsewhere, invasive impacts are often a case of risk perception rather than actual risk analysis. Two range-restricted headwater species, the Eastern Cape redfin Pseudobarbus afer and the Border barb Barbus trevelyani are redlisted by the International Union for the Conservation of Nature (IUCN) as ‘Endangered’, primarily due to invasion by non-native fishes. To investigate invasions in South Africa, and provide a quantitative estimate of the impact of non-native fishes on the two imperilled endemics, P. afer and B. trevelyani, the overall aims of this thesis were to: (A) Provide a literature review on non-native fish invasions in South Africa; (B) Using two case studies on the headwaters of the perennial Keiskamma and episodic Swartkops River systems, investigate the naturalisation-invasion continuum to provide a holistic view of the invasion process in these variable environments. The specific thesis objectives were: (1) Reviewing current knowledge of invasive impacts of non-native fishes in South Africa; (2) Investigating invasibility of headwater stream environments by non-native fishes; (3) Determining the establishment success of non-native fishes, (4) Assessing the spatial and temporal impacts of invasion; (5) Understanding mechanisms responsible for non-native fish impacts; (6) Investigating the threat of non-native fish invasion on the genetic diversity of two the two headwater fishes, P. afer and B. trevelyani. Results from the literature review of fish invasions (Chapter 1) showed that South Africa has a long history of non-native fish introductions, spanning two and a half centuries. Currently, 55 species have been introduced or translocated. Many of these introduced species have become fully invasive (36%). Their impacts also span multiple levels of biological organisation. There was a general paucity of studies on fish invasions (38 studies), however, of those conducted, reviewed studies placed emphases on invasive impacts (25 studies) and the transport, introduction, establishment and spread stages of the invasion process were largely ignored. The two study systems, the Swartkops and Keiskamma Rivers, were heavily invaded and numbers of introduced species surpassed that of natives (Chapter 2, 3 and 5). Headwater streams had varying invasibility and a number of non-native species were successfully established (Chapter 2, 3, 5 and 6). The remainder of the invasions were casual incursions into headwater streams from source populations in mainstream and impoundment environments which were invasion hotspots. Irrespective of establishment, four predatory invaders (largemouth bass Micropterus salmoides, smallmouth bass M. dolomieu, brown trout Salmo trutta and rainbow trout Oncorhynchus mykiss) impacted heavily on native fish communities (Chapter 3, 4 and 5). Two broad types of invasion were documented, top down invasion by non-native O. mykiss and S. trutta and upstream invasion by M. salmoides and M. dolomieu (Chapter 3 and 5). Their impacts included changes in community structure, extirpation from invaded stream reaches resulting in contracted distribution, and isolation and fragmentation of native fish populations. The impacts of non-native predatory fishes were particularly acute for P. afer and B. trevelyani. Where non-native predatory fish occurred, P. afer and B. trevelyani had been extirpated (Chapter 3 and 5). As a result both native species exhibited contracted distributions (>20% habitat loss due to invasion). Upstream invasion by centrarchids isolated and fragmented P. afer populations into headwater refugia, while top down invasion by salmonids excluded B. trevelyani from invaded, more pristine stream reaches, by forcing the species into degraded unsuitable lower stream reaches. Predation also disrupted population processes such as adult dispersal for P. afer, and centrarchid-invaded zones acted as demographic sinks, where adults dispersing through invaded reaches were rapidly depleted. While the Mandela lineage of P. afer exhibited little within or between drainage genetic structuring, B. trevelyani was >4% divergent between drainages, and up to 2% divergent between streams within the Keiskamma River system (Chapter 7). The distribution of genetic diversity for B. trevelyani also indicated that the loss of diversity was imminent without immediate conservation interventions. This thesis has provided conclusive evidence that native fishes are vulnerable to invasion and that non-native predatory fishes have significant impacts on native fishes in Eastern Cape headwater streams. If management and conservation measures are implemented, the unwanted introduction and spread of non-native fishes may be restricted, allowing native fishes opportunities for recovery.
- Full Text:
- Date Issued: 2014
- Authors: Ellender, Bruce Robert
- Date: 2014
- Subjects: Fishery management -- South Africa -- Eastern Cape Fishes -- Conservation -- South Africa Introduced fishes -- South Africa -- Eastern Cape Introduced organisms
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/69065 , vital:29380
- Description: The introduction, spread and concomitant impacts of non-native species are a global problem. Fish are among the most widely introduced vertebrate groups, with their impacts affecting multiple levels of organisation- from individuals, populations and communities, to entire ecosystems. In South Africa, the largest perceived threat to range-restricted endemic headwater stream fishes is said to be invasion by non-native fishes, however, as is the case elsewhere, invasive impacts are often a case of risk perception rather than actual risk analysis. Two range-restricted headwater species, the Eastern Cape redfin Pseudobarbus afer and the Border barb Barbus trevelyani are redlisted by the International Union for the Conservation of Nature (IUCN) as ‘Endangered’, primarily due to invasion by non-native fishes. To investigate invasions in South Africa, and provide a quantitative estimate of the impact of non-native fishes on the two imperilled endemics, P. afer and B. trevelyani, the overall aims of this thesis were to: (A) Provide a literature review on non-native fish invasions in South Africa; (B) Using two case studies on the headwaters of the perennial Keiskamma and episodic Swartkops River systems, investigate the naturalisation-invasion continuum to provide a holistic view of the invasion process in these variable environments. The specific thesis objectives were: (1) Reviewing current knowledge of invasive impacts of non-native fishes in South Africa; (2) Investigating invasibility of headwater stream environments by non-native fishes; (3) Determining the establishment success of non-native fishes, (4) Assessing the spatial and temporal impacts of invasion; (5) Understanding mechanisms responsible for non-native fish impacts; (6) Investigating the threat of non-native fish invasion on the genetic diversity of two the two headwater fishes, P. afer and B. trevelyani. Results from the literature review of fish invasions (Chapter 1) showed that South Africa has a long history of non-native fish introductions, spanning two and a half centuries. Currently, 55 species have been introduced or translocated. Many of these introduced species have become fully invasive (36%). Their impacts also span multiple levels of biological organisation. There was a general paucity of studies on fish invasions (38 studies), however, of those conducted, reviewed studies placed emphases on invasive impacts (25 studies) and the transport, introduction, establishment and spread stages of the invasion process were largely ignored. The two study systems, the Swartkops and Keiskamma Rivers, were heavily invaded and numbers of introduced species surpassed that of natives (Chapter 2, 3 and 5). Headwater streams had varying invasibility and a number of non-native species were successfully established (Chapter 2, 3, 5 and 6). The remainder of the invasions were casual incursions into headwater streams from source populations in mainstream and impoundment environments which were invasion hotspots. Irrespective of establishment, four predatory invaders (largemouth bass Micropterus salmoides, smallmouth bass M. dolomieu, brown trout Salmo trutta and rainbow trout Oncorhynchus mykiss) impacted heavily on native fish communities (Chapter 3, 4 and 5). Two broad types of invasion were documented, top down invasion by non-native O. mykiss and S. trutta and upstream invasion by M. salmoides and M. dolomieu (Chapter 3 and 5). Their impacts included changes in community structure, extirpation from invaded stream reaches resulting in contracted distribution, and isolation and fragmentation of native fish populations. The impacts of non-native predatory fishes were particularly acute for P. afer and B. trevelyani. Where non-native predatory fish occurred, P. afer and B. trevelyani had been extirpated (Chapter 3 and 5). As a result both native species exhibited contracted distributions (>20% habitat loss due to invasion). Upstream invasion by centrarchids isolated and fragmented P. afer populations into headwater refugia, while top down invasion by salmonids excluded B. trevelyani from invaded, more pristine stream reaches, by forcing the species into degraded unsuitable lower stream reaches. Predation also disrupted population processes such as adult dispersal for P. afer, and centrarchid-invaded zones acted as demographic sinks, where adults dispersing through invaded reaches were rapidly depleted. While the Mandela lineage of P. afer exhibited little within or between drainage genetic structuring, B. trevelyani was >4% divergent between drainages, and up to 2% divergent between streams within the Keiskamma River system (Chapter 7). The distribution of genetic diversity for B. trevelyani also indicated that the loss of diversity was imminent without immediate conservation interventions. This thesis has provided conclusive evidence that native fishes are vulnerable to invasion and that non-native predatory fishes have significant impacts on native fishes in Eastern Cape headwater streams. If management and conservation measures are implemented, the unwanted introduction and spread of non-native fishes may be restricted, allowing native fishes opportunities for recovery.
- Full Text:
- Date Issued: 2014