The effects of environmental variability on the physiology and ecology of Cape stumpnose Rhabdosargus holubi (Steindachner, 1881) (Sparidae)
- Authors: Kisten, Yanasivan
- Date: 2018
- Subjects: Freshwater fishes -- South Africa , Fishes -- Ecology Freshwater fishes -- Ecology Estuarine ecology -- South Africa Estuaries -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/31424 , vital:31374
- Description: Estuaries are important nursery areas for early stages of marine estuarine-dependent fishes, such as the sparid Rhabdosargus holubi. Estuaries provide food, shelter from predators and optimal habitats and environmental conditions for growth and development. However, estuaries are environmentally dynamic and resident organisms must be able to adapt to rapid changes. Such changes are potentially further exacerbated anthropogenically by water and land use practices such as freshwater abstraction, impoundment, pollution and anthropogenically driven climatic change. An effective approach to better understanding the current and future impacts of these kinds of changes, is by assessing the environmental adaptability of organisms, especially to extreme conditions such as droughts and resulting water shortages, which are prevalent in some parts of southern Africa. This thesis examines the effect of various environmental changes such as salinity, turbidity and temperature on the ecology and physiology of a South African common endemic fish species, the Cape stumpnose, R. holubi. Previous work on the species have investigated short term impacts on physiology while this study investigates medium to short term impacts. The specie’s wide distribution in South Africa and tolerance enabled a range of environmental, ecological and physiological relationships to be tested in the context of a changing world. These included: 1) determining the relationship between environmental variability and the distribution and abundance of R. holubi larvae in 25 estuaries along the temperate coast of South Africa; 2) determining the relationship between environmental variability and the movement of larvae and juveniles within two permanently open estuaries; 3) determining the impact of shock and acclimatization on R. holubi salinity tolerance ranges under hypersaline conditions; 4) II determining the impact of hypersalinity on the potential long term impacts growth and skeletal deformities of juvenile R. holubi in aquaria. The findings of these studies suggest that larval occurrence and density within estuaries is a function of salinity and turbidity, by proxy indicating a preference for high freshwater inflow especially in estuary types such as permanently open estuaries. The movement of larvae and juveniles within these estuaries is also mediated by salinity, turbidity and temperature, indicating the importance of seasonality along with environmental conditions and potential olfactory recruitment cues driven by freshwater flow. Tolerance experiments showed that slower acclimation to higher salinities can expand the previously reported tolerance range indicating the potential for adaptation. Physiological experiments showed negative impacts on respiration at salinities exceeding 45, indicating potential long-term physiological effects in hypersaline conditions. Further, living at high salinities for extended periods may have potentially negative effects on long term physiology, particularly growth and skeletal development. The overall results indicate that low salinity (5–18), high turbidity (20–30 NTU) and high temperature (5–22°C) are integral to the distribution and abundance of the species in permanently open estuaries. This conforms to the general rule that estuarine-associated marine fish have higher growth rates in salinities of 12-19. However, juveniles are also adapted to survive at higher salinities for long periods (2 months in the current thesis). This explains why R. holubi is one of the few species in the estuarine fish community that may persist during droughts. The predicted future changes in coastal temperatures and rainfall by climate change investigators, are likely to result in range shifts and changes in recruitment times of estuarine fish communities. The current work addresses novel aspects of the ecology and physiology of R. holubi and indicates that this species will play an increasingly important role within the estuaries of South Africa.
- Full Text:
- Date Issued: 2018
- Authors: Kisten, Yanasivan
- Date: 2018
- Subjects: Freshwater fishes -- South Africa , Fishes -- Ecology Freshwater fishes -- Ecology Estuarine ecology -- South Africa Estuaries -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/31424 , vital:31374
- Description: Estuaries are important nursery areas for early stages of marine estuarine-dependent fishes, such as the sparid Rhabdosargus holubi. Estuaries provide food, shelter from predators and optimal habitats and environmental conditions for growth and development. However, estuaries are environmentally dynamic and resident organisms must be able to adapt to rapid changes. Such changes are potentially further exacerbated anthropogenically by water and land use practices such as freshwater abstraction, impoundment, pollution and anthropogenically driven climatic change. An effective approach to better understanding the current and future impacts of these kinds of changes, is by assessing the environmental adaptability of organisms, especially to extreme conditions such as droughts and resulting water shortages, which are prevalent in some parts of southern Africa. This thesis examines the effect of various environmental changes such as salinity, turbidity and temperature on the ecology and physiology of a South African common endemic fish species, the Cape stumpnose, R. holubi. Previous work on the species have investigated short term impacts on physiology while this study investigates medium to short term impacts. The specie’s wide distribution in South Africa and tolerance enabled a range of environmental, ecological and physiological relationships to be tested in the context of a changing world. These included: 1) determining the relationship between environmental variability and the distribution and abundance of R. holubi larvae in 25 estuaries along the temperate coast of South Africa; 2) determining the relationship between environmental variability and the movement of larvae and juveniles within two permanently open estuaries; 3) determining the impact of shock and acclimatization on R. holubi salinity tolerance ranges under hypersaline conditions; 4) II determining the impact of hypersalinity on the potential long term impacts growth and skeletal deformities of juvenile R. holubi in aquaria. The findings of these studies suggest that larval occurrence and density within estuaries is a function of salinity and turbidity, by proxy indicating a preference for high freshwater inflow especially in estuary types such as permanently open estuaries. The movement of larvae and juveniles within these estuaries is also mediated by salinity, turbidity and temperature, indicating the importance of seasonality along with environmental conditions and potential olfactory recruitment cues driven by freshwater flow. Tolerance experiments showed that slower acclimation to higher salinities can expand the previously reported tolerance range indicating the potential for adaptation. Physiological experiments showed negative impacts on respiration at salinities exceeding 45, indicating potential long-term physiological effects in hypersaline conditions. Further, living at high salinities for extended periods may have potentially negative effects on long term physiology, particularly growth and skeletal development. The overall results indicate that low salinity (5–18), high turbidity (20–30 NTU) and high temperature (5–22°C) are integral to the distribution and abundance of the species in permanently open estuaries. This conforms to the general rule that estuarine-associated marine fish have higher growth rates in salinities of 12-19. However, juveniles are also adapted to survive at higher salinities for long periods (2 months in the current thesis). This explains why R. holubi is one of the few species in the estuarine fish community that may persist during droughts. The predicted future changes in coastal temperatures and rainfall by climate change investigators, are likely to result in range shifts and changes in recruitment times of estuarine fish communities. The current work addresses novel aspects of the ecology and physiology of R. holubi and indicates that this species will play an increasingly important role within the estuaries of South Africa.
- Full Text:
- Date Issued: 2018
Implementation of performance management systems at the South African Social Security Agency (SASSA), Nelson Mandela Metro District
- Authors: Nabo, Vuyokazi
- Date: 2014
- Subjects: Performance standards -- South Africa -- Nelson Mandela Bay Municipality , Performance -- Management -- Evaluation , Performance -- Measurement , Employees -- Rating of -- South Africa -- Nelson Mandela Bay Municipality
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/6412 , vital:21083
- Description: The focus of the study is to investigate the factors that impact on effective implementation of a performance management system at the South African Social Security Agency (SASSA) in the Eastern Cape Region, Nelson Mandela Metro District. It is said that an organisational success in service delivery largely depends on the efficiency and effectiveness of its employees in undertaking their functions, duties and responsibilities (Ntombela, Mpehle and Penciliah, 2010: 63).
- Full Text:
- Date Issued: 2014
- Authors: Nabo, Vuyokazi
- Date: 2014
- Subjects: Performance standards -- South Africa -- Nelson Mandela Bay Municipality , Performance -- Management -- Evaluation , Performance -- Measurement , Employees -- Rating of -- South Africa -- Nelson Mandela Bay Municipality
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/6412 , vital:21083
- Description: The focus of the study is to investigate the factors that impact on effective implementation of a performance management system at the South African Social Security Agency (SASSA) in the Eastern Cape Region, Nelson Mandela Metro District. It is said that an organisational success in service delivery largely depends on the efficiency and effectiveness of its employees in undertaking their functions, duties and responsibilities (Ntombela, Mpehle and Penciliah, 2010: 63).
- Full Text:
- Date Issued: 2014
A post restucturing assessment of employee attitudes in South African National Science Council
- Authors: Bugaari, Lynn
- Date: 2012
- Subjects: Job enrichment , Employees -- Attitudes , Employee morale , Performance standards
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:9945 , http://hdl.handle.net/10948/d1013702
- Description: Research problem: The restructuring of an organisation can be classified as a transformational intervention (Litwin & Burke, 1992). As such is it has a potential to significantly influence key employee attitudes that are related to employee and organisational performance. Any deterioration in these attitudes could impact negatively on organisational outcomes. As part of the monitoring and review of change interventions, management needs to understand the change in employee attitudes towards their work and management in their business units and towards the broader organisation in order that, if necessary, corrective action can be taken. Research objectives: To address the research problem, research objectives and questions were established. The main objective of the study was to investigate whether there has been a change in attitudes of employees in two business units of a South African National Science Council after the implementation of restructuring in the organisation and the business units. The key attitudes to be measured are job and management satisfaction, perceived organisational support, organisational commitment and a dimension of employee engagement, dedication. Research questions: Four research questions were established and these were; What is the change in employee attitudes post-restructuring? In particular what is the change in employee job satisfaction; management satisfaction, employee engagement, commitment to the organisation and perceived organisational support? What is the relationship between the sub-groups, distinguished by gender, occupational level, race, home language, age, number of years of service and business unit, and employee attitudes pre-restructuring? What is the relationship between the sub-groups distinguished by gender, occupational level, race, home language, age, number of years of service and business unit, and employee attitudes post-restructuring? What is the relationship between the sub-groups distinguished by gender, occupational level, race, home language, age, number of years of service and business unit, and the change in employee attitudes pre and post-restructuring? Research design: The nature of this research is descriptive. In order to solve the research questions the researcher used a pre-test and post-test measurement of employee attitudes. A survey using a structured self-administered questionnaire was used to collect information regarding employee attitudes before and after the restructuring of the organisation and business units. Major findings: The results from the survey showed that there was a change in the levels of organisational commitment, job satisfaction and management satisfaction at the National Science Council after the restructuring had taken place. Also, the impact of the sub-groups in the organisation on affective factors was evident in the level of occupation and employee engagement, race and management satisfaction, the business unit and the levels of perceived organisational support, management satisfaction and employee engagement, home language and employee engagement, the number of years the employee had worked for the organisation and management satisfaction, age and job satisfaction and employee engagement.
- Full Text:
- Date Issued: 2012
- Authors: Bugaari, Lynn
- Date: 2012
- Subjects: Job enrichment , Employees -- Attitudes , Employee morale , Performance standards
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:9945 , http://hdl.handle.net/10948/d1013702
- Description: Research problem: The restructuring of an organisation can be classified as a transformational intervention (Litwin & Burke, 1992). As such is it has a potential to significantly influence key employee attitudes that are related to employee and organisational performance. Any deterioration in these attitudes could impact negatively on organisational outcomes. As part of the monitoring and review of change interventions, management needs to understand the change in employee attitudes towards their work and management in their business units and towards the broader organisation in order that, if necessary, corrective action can be taken. Research objectives: To address the research problem, research objectives and questions were established. The main objective of the study was to investigate whether there has been a change in attitudes of employees in two business units of a South African National Science Council after the implementation of restructuring in the organisation and the business units. The key attitudes to be measured are job and management satisfaction, perceived organisational support, organisational commitment and a dimension of employee engagement, dedication. Research questions: Four research questions were established and these were; What is the change in employee attitudes post-restructuring? In particular what is the change in employee job satisfaction; management satisfaction, employee engagement, commitment to the organisation and perceived organisational support? What is the relationship between the sub-groups, distinguished by gender, occupational level, race, home language, age, number of years of service and business unit, and employee attitudes pre-restructuring? What is the relationship between the sub-groups distinguished by gender, occupational level, race, home language, age, number of years of service and business unit, and employee attitudes post-restructuring? What is the relationship between the sub-groups distinguished by gender, occupational level, race, home language, age, number of years of service and business unit, and the change in employee attitudes pre and post-restructuring? Research design: The nature of this research is descriptive. In order to solve the research questions the researcher used a pre-test and post-test measurement of employee attitudes. A survey using a structured self-administered questionnaire was used to collect information regarding employee attitudes before and after the restructuring of the organisation and business units. Major findings: The results from the survey showed that there was a change in the levels of organisational commitment, job satisfaction and management satisfaction at the National Science Council after the restructuring had taken place. Also, the impact of the sub-groups in the organisation on affective factors was evident in the level of occupation and employee engagement, race and management satisfaction, the business unit and the levels of perceived organisational support, management satisfaction and employee engagement, home language and employee engagement, the number of years the employee had worked for the organisation and management satisfaction, age and job satisfaction and employee engagement.
- Full Text:
- Date Issued: 2012
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