Early stage ichthyofauna from shallow water habitats of the Angola-Benguela frontal zone
- Authors: Farthing, Matthew William
- Date: 2017
- Subjects: Fishes -- Larvae -- South Africa -- Atlantic coast , Fishes -- Larvae -- Angola -- Atlantic coast , Striped mullet -- Angola -- Atlantic coast
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/50442 , vital:25988
- Description: Early stage fishes (larvae and early juveniles) were collected from an array of shallow water (±1.5m) habitats on the warm-temperate southern Angolan coastline between June 2014 and June 2015. This study, the first assessment of the early stages of coastal fishes in Angola, provides important new understanding of non-estuarine shallow water nursery habitat use by coastal fishes from the region. In total, 51 species from 18 teleost families were observed. The exposed surf zone was dominated by postflexion larvae, while the moderately exposed beach and sheltered bay were dominated by early juveniles. Both fish density and diversity peaked in the wet season (Feb – Apr 2015) for all habitats, attributed to the influx of summer spawning species. Diplodus sargus dominated catches from the exposed surf zone, and the timing of observations supports the growing consensus that sparid spawning is dictated by temperature, not season. The similitude of the observed species to those observed in warm temperate South Africa highlights the historical connection of the warm-temperate study area with warm-temperate South Africa, prior to the formation of the Benguela Current as a vicariant barrier. The classification of the study assemblage into established estuarine utilization categories showed that the surf zone hosted more exclusively marine species than comparable surf zones in South Africa, attributed to the absence of estuaries in southern Angola. However, the observation of the marine estuarine dependent Mugil cephalus in this study area devoid of estuaries suggests that estuarine dependency may be regionally specific for some taxa. It appears that the warm, sheltered, nutrient rich waters of Tombua Bay provide typically estuarine associated taxa with a suitable alternative, non-estuarine nursery habitat. This study provides evidence that the importance of estuaries as critical nursery habitats has been overemphasized for some warm-temperate coastal fishes. However, the absence of other marine estuarine dependent species from the study area suggests that some warm-temperate taxa do intrinsically rely on estuarine function for survival.
- Full Text:
- Date Issued: 2017
- Authors: Farthing, Matthew William
- Date: 2017
- Subjects: Fishes -- Larvae -- South Africa -- Atlantic coast , Fishes -- Larvae -- Angola -- Atlantic coast , Striped mullet -- Angola -- Atlantic coast
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/50442 , vital:25988
- Description: Early stage fishes (larvae and early juveniles) were collected from an array of shallow water (±1.5m) habitats on the warm-temperate southern Angolan coastline between June 2014 and June 2015. This study, the first assessment of the early stages of coastal fishes in Angola, provides important new understanding of non-estuarine shallow water nursery habitat use by coastal fishes from the region. In total, 51 species from 18 teleost families were observed. The exposed surf zone was dominated by postflexion larvae, while the moderately exposed beach and sheltered bay were dominated by early juveniles. Both fish density and diversity peaked in the wet season (Feb – Apr 2015) for all habitats, attributed to the influx of summer spawning species. Diplodus sargus dominated catches from the exposed surf zone, and the timing of observations supports the growing consensus that sparid spawning is dictated by temperature, not season. The similitude of the observed species to those observed in warm temperate South Africa highlights the historical connection of the warm-temperate study area with warm-temperate South Africa, prior to the formation of the Benguela Current as a vicariant barrier. The classification of the study assemblage into established estuarine utilization categories showed that the surf zone hosted more exclusively marine species than comparable surf zones in South Africa, attributed to the absence of estuaries in southern Angola. However, the observation of the marine estuarine dependent Mugil cephalus in this study area devoid of estuaries suggests that estuarine dependency may be regionally specific for some taxa. It appears that the warm, sheltered, nutrient rich waters of Tombua Bay provide typically estuarine associated taxa with a suitable alternative, non-estuarine nursery habitat. This study provides evidence that the importance of estuaries as critical nursery habitats has been overemphasized for some warm-temperate coastal fishes. However, the absence of other marine estuarine dependent species from the study area suggests that some warm-temperate taxa do intrinsically rely on estuarine function for survival.
- Full Text:
- Date Issued: 2017
Oxygen limitation and thermal tolerance: a comparison of pulmonate and patellogastropod limpets
- Authors: Kankondi, Sebbi
- Date: 2017
- Subjects: Thermal tolerance (Physiology) , Limpets -- Physiology , Limpets -- Effect of temperature on , Oxygen consumption (Physiology)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7570 , vital:21274
- Description: Since the scientific community anticipates a general change in the global climate, it has become increasingly important to develop predictive models which encompass mechanisms to generate reliable forecasts of the effects this change on ecological communities and processes. To this end, the oxygen- and capacity- limited thermal tolerance (OCLTT) theory has been developed as a link between various physiological processes, the thermal aspect of climate change and the associated shifts at different levels of biological organization. This study set out to assess the general applicability of the OCLTT theory in eurythermal pulmonate and patellogastropod limpets, whose distributions overlap on the high shore rocks of the warm temperate, south-east coast of South Africa.This was done by determining their microhabitat use, median lethal temperatures and cardiac, Arrhenius breakpoint temperatures as measures of their upper thermal tolerance limits, in both air and water. The main hypotheses of the study were that the pulmonate limpets would be more common than the patellogastropods in warmer microhabitats during low tide and would have higher thermal limits than the patellogastropods in air and vice versa in water. This was based on the assumption that the two limpet groups have different capabilities of oxygen consumption in air and water, due to differences in their respiratory organs and that this would be reflected in their thermal tolerances based on predictions made by the OCLTT. This assumption was important because oxygen consumption was not measured in this study. Previous research (e.g. Garrity, 1984), showed that a thermal stress gradient exists among rocky intertidal microhabitats. From most to least thermally stressful the gradient is horizontal surfaces> slopes> vertical surfaces> tide pools> crevices. The current study found that, while the pulmonate limpets, Siphonaria capensis and S. serrata, preferred rock pools, sloped, vertical and horizontal rock surfaces, the patellogastropod limpets, Cellana capensis and Scutellastra granularis, preferred rock pools and vertical rock surfaces. Furthermore, the pulmonate limpets were only common on horizontal rock surfaces where specific ameliorating conditions would have mitigated thermal stress there. In addition, C. capensis had similar thermal tolerance limits to the pulmonate limpets in air and the pulmonate limpets had similar and/or higher thermal tolerance limits compared to S. granularis in water. This indicates that the pulmonate limpets did not necessarily prefer warmer microhabitats than the patellogastropod limpets and that there were no differences in the collective upper thermal tolerance limits between the two limpet groups in either medium.Consequently, there was no indication from this study that an assumed superior capacity for oxygen supply translates into greater thermal tolerance and that the hypotheses based on the OCLTT were not supported. Although this was an indirect test of the OCLTT theory, I conclude that this study does not support the notion of its general applicability and that mechanisms other than those outlined by the OCLTT theory may help explain the patterns of thermal limitation observed in the current study.
- Full Text:
- Date Issued: 2017
- Authors: Kankondi, Sebbi
- Date: 2017
- Subjects: Thermal tolerance (Physiology) , Limpets -- Physiology , Limpets -- Effect of temperature on , Oxygen consumption (Physiology)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7570 , vital:21274
- Description: Since the scientific community anticipates a general change in the global climate, it has become increasingly important to develop predictive models which encompass mechanisms to generate reliable forecasts of the effects this change on ecological communities and processes. To this end, the oxygen- and capacity- limited thermal tolerance (OCLTT) theory has been developed as a link between various physiological processes, the thermal aspect of climate change and the associated shifts at different levels of biological organization. This study set out to assess the general applicability of the OCLTT theory in eurythermal pulmonate and patellogastropod limpets, whose distributions overlap on the high shore rocks of the warm temperate, south-east coast of South Africa.This was done by determining their microhabitat use, median lethal temperatures and cardiac, Arrhenius breakpoint temperatures as measures of their upper thermal tolerance limits, in both air and water. The main hypotheses of the study were that the pulmonate limpets would be more common than the patellogastropods in warmer microhabitats during low tide and would have higher thermal limits than the patellogastropods in air and vice versa in water. This was based on the assumption that the two limpet groups have different capabilities of oxygen consumption in air and water, due to differences in their respiratory organs and that this would be reflected in their thermal tolerances based on predictions made by the OCLTT. This assumption was important because oxygen consumption was not measured in this study. Previous research (e.g. Garrity, 1984), showed that a thermal stress gradient exists among rocky intertidal microhabitats. From most to least thermally stressful the gradient is horizontal surfaces> slopes> vertical surfaces> tide pools> crevices. The current study found that, while the pulmonate limpets, Siphonaria capensis and S. serrata, preferred rock pools, sloped, vertical and horizontal rock surfaces, the patellogastropod limpets, Cellana capensis and Scutellastra granularis, preferred rock pools and vertical rock surfaces. Furthermore, the pulmonate limpets were only common on horizontal rock surfaces where specific ameliorating conditions would have mitigated thermal stress there. In addition, C. capensis had similar thermal tolerance limits to the pulmonate limpets in air and the pulmonate limpets had similar and/or higher thermal tolerance limits compared to S. granularis in water. This indicates that the pulmonate limpets did not necessarily prefer warmer microhabitats than the patellogastropod limpets and that there were no differences in the collective upper thermal tolerance limits between the two limpet groups in either medium.Consequently, there was no indication from this study that an assumed superior capacity for oxygen supply translates into greater thermal tolerance and that the hypotheses based on the OCLTT were not supported. Although this was an indirect test of the OCLTT theory, I conclude that this study does not support the notion of its general applicability and that mechanisms other than those outlined by the OCLTT theory may help explain the patterns of thermal limitation observed in the current study.
- Full Text:
- Date Issued: 2017
A risk-based framework for new products: a South African telecommunication’s study
- Authors: Jeffries, Michael
- Date: 2017
- Subjects: Telephone companies -- Risk management -- South Africa , Telephone companies -- South Africa -- Case studies , Telecommunication -- Security measures -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4765 , vital:20722
- Description: The integrated reports of Vodacom, Telkom and MTN — telecommunication organisations in South Africa — show that they are diversifying their product offerings from traditional voice and data services. These organisations are including new offerings covering the financial, health, insurance and mobile education services. The potential exists for these organisations to launch products that are substandard and which either do not take into account customer needs or do not comply with current legislations or regulations. Most telecommunication organisations have a well-defined enterprise risk management program, to ensure compliance to King III, however risk management processes specifically for new products and services might be lacking. The responsibility usually resides with the product managers for the implementation of robust products; however they do not always have the correct skillset to ensure adherence to governance requirements and therefore might not be aware of which laws they might not be adhering to, or understand the customers’ requirements. More complex products, additional competition, changes to technology and new business ventures have reinforced the need to manage risk on telecommunication products. Failure to take risk requirements into account could lead to potential fines, damage the organisation’s reputation which could lead to customers churning from these service providers. This research analyses three periods of data captured from a mobile telecommunication organisation to assess the current status quo of risk management maturity within the organisation’s product and service environment. Based on the analysis as well as industry best practices, a risk management framework for products is proposed that can assist product managers analyse concepts to ensure adherence to governance requirements. This could assist new product or service offerings in the marketplace do not create a perception of distrust by consumers.
- Full Text:
- Date Issued: 2017
- Authors: Jeffries, Michael
- Date: 2017
- Subjects: Telephone companies -- Risk management -- South Africa , Telephone companies -- South Africa -- Case studies , Telecommunication -- Security measures -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4765 , vital:20722
- Description: The integrated reports of Vodacom, Telkom and MTN — telecommunication organisations in South Africa — show that they are diversifying their product offerings from traditional voice and data services. These organisations are including new offerings covering the financial, health, insurance and mobile education services. The potential exists for these organisations to launch products that are substandard and which either do not take into account customer needs or do not comply with current legislations or regulations. Most telecommunication organisations have a well-defined enterprise risk management program, to ensure compliance to King III, however risk management processes specifically for new products and services might be lacking. The responsibility usually resides with the product managers for the implementation of robust products; however they do not always have the correct skillset to ensure adherence to governance requirements and therefore might not be aware of which laws they might not be adhering to, or understand the customers’ requirements. More complex products, additional competition, changes to technology and new business ventures have reinforced the need to manage risk on telecommunication products. Failure to take risk requirements into account could lead to potential fines, damage the organisation’s reputation which could lead to customers churning from these service providers. This research analyses three periods of data captured from a mobile telecommunication organisation to assess the current status quo of risk management maturity within the organisation’s product and service environment. Based on the analysis as well as industry best practices, a risk management framework for products is proposed that can assist product managers analyse concepts to ensure adherence to governance requirements. This could assist new product or service offerings in the marketplace do not create a perception of distrust by consumers.
- Full Text:
- Date Issued: 2017
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