The assessment and management of bycatch and discards in the South African demersal trawl fishery
- Authors: Walmsley, Sarah Ann
- Date: 2005
- Subjects: Bycatches (Fisheries) Fishery management -- South Africa Fisheries -- South Africa Trawls and trawling -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5228 , http://hdl.handle.net/10962/d1005071
- Description: Over the past few decades it has become recognised that an ecosystem approach is required to manage world fisheries. Management strategies must ensure that non-target (bycatch) as well as target catches are sustainable. To achieve this, detailed commercial catch and biological information is required. The composition of catches made by trawlers operating off the south and west coasts of South Africa was investigated. Distinct fishing areas were identified on each coast, based on target species and fishing depth. Catch composition differed markedly among the areas defined. Although hake Merluccius sp. dominated South Coast catches, a large proportion of the catch was composed of bycatch. On the West Coast, hake dominated catches and this domination increased with increasing depth. On both coasts approximately 90% of the observed nominal catch was processed and landed. Estimates of annual discards suggested that the fishery discarded 38 thousand tons of fish per annum (16% of the nominal trawl catch). The data also indicated that hake discarding, the capture of linefish and the increased targeting of high value species might be cause for concern. Spatial analysis indicated that a variety of factors such as trawling position, catch size and catch composition affects bycatch dynamics. The monkfish Lophius vomerinus is a common bycatch species that has been increasingly targeted by demersal trawlers. This study showed that L. vomerinus is a slow-growing, long-lived species (West Coast males L∞ = 68.50cm TL, t₀ = -1.69yr, K = 0.10yr⁻¹; West Coast females L∞ = 110.23cm TL, t₀ = -1.54yr, K = 0.05yr⁻¹; South Coast sexes combined L∞ = 70.12cm TL, t₀ = - 0.80yr, K = 0.11yr⁻¹), that matures at approximately 6 years of age. These traits could have serious management implications for the species. Per-recruit analysis suggested that the stock might be overexploited, although further investigation is required to confirm this. Solutions were suggested for each of the concerns raised, taking cognisance of the differences observed between the South and West Coasts and the economic dependence of South Coast companies on bycatch. The needs of future research were considered.
- Full Text:
- Date Issued: 2005
- Authors: Walmsley, Sarah Ann
- Date: 2005
- Subjects: Bycatches (Fisheries) Fishery management -- South Africa Fisheries -- South Africa Trawls and trawling -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5228 , http://hdl.handle.net/10962/d1005071
- Description: Over the past few decades it has become recognised that an ecosystem approach is required to manage world fisheries. Management strategies must ensure that non-target (bycatch) as well as target catches are sustainable. To achieve this, detailed commercial catch and biological information is required. The composition of catches made by trawlers operating off the south and west coasts of South Africa was investigated. Distinct fishing areas were identified on each coast, based on target species and fishing depth. Catch composition differed markedly among the areas defined. Although hake Merluccius sp. dominated South Coast catches, a large proportion of the catch was composed of bycatch. On the West Coast, hake dominated catches and this domination increased with increasing depth. On both coasts approximately 90% of the observed nominal catch was processed and landed. Estimates of annual discards suggested that the fishery discarded 38 thousand tons of fish per annum (16% of the nominal trawl catch). The data also indicated that hake discarding, the capture of linefish and the increased targeting of high value species might be cause for concern. Spatial analysis indicated that a variety of factors such as trawling position, catch size and catch composition affects bycatch dynamics. The monkfish Lophius vomerinus is a common bycatch species that has been increasingly targeted by demersal trawlers. This study showed that L. vomerinus is a slow-growing, long-lived species (West Coast males L∞ = 68.50cm TL, t₀ = -1.69yr, K = 0.10yr⁻¹; West Coast females L∞ = 110.23cm TL, t₀ = -1.54yr, K = 0.05yr⁻¹; South Coast sexes combined L∞ = 70.12cm TL, t₀ = - 0.80yr, K = 0.11yr⁻¹), that matures at approximately 6 years of age. These traits could have serious management implications for the species. Per-recruit analysis suggested that the stock might be overexploited, although further investigation is required to confirm this. Solutions were suggested for each of the concerns raised, taking cognisance of the differences observed between the South and West Coasts and the economic dependence of South Coast companies on bycatch. The needs of future research were considered.
- Full Text:
- Date Issued: 2005
The biophysical dynamics of the Lower Shire River Floodplain fisheries in Malawi
- Authors: Chimatiro, Sloans Kalumba
- Date: 2005
- Subjects: Shire River Valley (Malawi and Mozambique) Fisheries -- Malawi
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5243 , http://hdl.handle.net/10962/d1005086
- Description: Fishes of African floodplains typically comprise populations having short life cycles, relatively few age groups, more generalised feeding behaviour, and which experience spawning success that is strongly influenced by abiotic factors such as hydrological regime of the river, climatic seasonality and habitat characteristics. In addition, African river-floodplain ecosystems do not have appropriate predictive models for estimating yield in these ecosystems. While most predictive models developed to date for floodplain fisheries have taken into account morpho-edaphic factors, they have generally excluded climatic factors as a mega-determinant of the variability of floodplain fisheries. The principle aim of this thesis has been to develop a predictive management model that incorporates data on essential biological aspects of the target species, characteristics of the habitat as well as overall climatic factors, and thus allow for adaptive management of the fisheries in a continuously fluctuating floodplain environment. Lower Shire Floodplain (34 ⁰ 45’ – 35 ⁰ E and 16 ⁰ 00’-17 ⁰ 15’ S) in Malawi, one of the major rivers-floodplains in the Zambezi Basin, was used to test this type of model. The major hypothesis tested in this study was that “the dynamics of the fishery of Lower Shire Floodplain are driven by and adapted to the seasonal, but predictable, hydro-climatic regime of the floodplain”. The specific objectives were: to describe the floodplain’s climate and hydrological pattern; to develop a quantitative characterisation of the major habitats of the Lower Shire Floodplain; to assess the fishery in terms of size, gear utilisation, gear selectivity and yield; to assess the biological parameters of the target species, necessary for the management of the fishery; to analyse how water fluctuation in the floodplain affects the recruitment and life history of the two target species; and to develop of a predictive hydro-climatic model to benefit the management of the fisheries. The climate of the floodplain was characterised by low (765 ± 198 mm) and fairly variable (Cv = 27%) rainfall, which largely occurred between December and January. The area was generally humid (mean RH 68%), with mild to hot (25- 33ºC) and variable monthly mean diurnal (12ºC) temperature. Four quarterly hydro-climatic seasons were identified and comprised: Quarter 1 (Jul-Sep) characterised by hot, dry weather with a low flood regime; Quarter 2 (Oct-Dec) hot, windy, wet weather with low-but-rising flood regime; Quarter 3 (Jan-Mar) hot humid, wet weather with the flood regime at peak; and Quarter 4 (Apr-Jun) humid and cool weather with receding flood regime. The annual hydrograph of the floodplain was represented by four categories of flood regime as: low (Jul-Sept), low-but-rising (Oct-Dec), peak (Jan- Mar), and falling (Apr-Jun). The floodplain experienced a water deficit of 95.1 mm.year⁻¹, and it was hypothesised that ground water recharge maintained water in the floodplain the rest of the year. Three major habitats were identified in the floodplain. The river-floodplain, characterised by deep fast-flowing water, sandy substrate and little emergent vegetation; the permanently connected lagoons, were shallow (≤ 2 m) with sandymud bottom and slow flowing water; and the seasonally connected lagoons had slowflowing stagnant water, with comparatively more emergent and floating vegetation. Physicochemical characteristics of the habitats varied significantly with hydroclimatic seasons (one-way ANOVA, p ≤ 0.05), indicating the influence of flood regime, which joined the habitats in a non-equilibrial spatial distribution. Consequently, during receding and low flood regimes river-floodplain and permanently connected lagoons exhibited similar characteristics while all three habitats had similar characteristics during the rising and peak flood regimes. It was, therefore, concluded that in floodplains, habitats shift horizontally and vertically according to the water level. Gill nets, cast nets, long line, and fish traps accounted for 99% of the total count of gears, and hence considered the major fishing sectors. Two principal species in the floodplain were the catfish Clarias gariepinus and the cichlid Oreochromis mossambicus. Length-at-maximum-selectivity (ø) and length-at-50%-sexual-maturity (Lm₅₀) for each of the two species showed that although they were selected into the four fishing sectors at lengths above maturity, maximum selectivity into the long line occurred at a length before maturity for O. mossambicus. In addition, the width of the gamma selectivity function (σ) indicated that a considerable proportion of juveniles of the two species were also selected. Therefore, it was decided that management for the floodplain be centred on controlling over-fishing and preserving the spawner stock, by banning seine and mosquito nets, and closing river-floodplain and permanently connected lagoons to fishing during the low flood regime. There were significant seasonal variations in CPUE, lowest in the low flood, and highest during the peak flood regime. Sectioned otoliths were used to determine the age and growth of the two principal species in the floodplain. Marginal zone analysis revealed that annulus formation in all the species occurred during the period of low air and water temperatures, high evaporation and receding water levels, hence a high rate of desiccation and negative water budget. For O. mossambicus, maximum age reached was 6 years while in C. gariepinus it was 9 years. The 3-parameter von Bertalanffy growth model adequately described growth as lt = 177.6(1-e⁻·⁴⁴⁽t ⁺ ¹·⁴³⁾) mm TL for O. mossambicus and lt = 502.9(1-e⁻°·³¹⁽t ⁺ ¹·⁹²⁾) mm TL for C. gariepinus. Female O. mossambicus reached 50%-sexual-maturity at 109 mm SL, while males matured at 105 mm, and both male and female C. gariepinus reached Lm₅₀ at 249 mm SL. The breeding seasons of both O. mossambicus and Clarias gariepinus were between September and March, with modal peaks in January and November, respectively. The annual total mortality rates (Z) were 0.62 ± 0.18 yr⁻¹ for O. mossambicus and 0.93 ± 0.47 yr⁻¹ for C. gariepinus. The mean empirical estimates of natural mortality (M) were 0.46 yr⁻¹ for O. mossambicus and 0.50 year⁻¹ for C. gariepinus, and fishing mortality (F) was calculated as 0.16 yr⁻¹ for O. mossambicus and 0.43 yr⁻¹ for C. gariepinus. The overall exploitation level (Z/K) was 1.41 for O. mossambicus and 3.01 for C. gariepinus. Given that the Z/K ratio was >1, it was asserted that both O. mossambicus and C. gariepinus were mortality-dominated and fairly heavily exploited. However, potential for sustainable exploitation existed since both species showed signs of resilience due short longevity and high rate of natural mortality. Given the limitation of simple exponential models of fish mortality and growth under the situation of seasonal fluctuation of water levels, a simple predictive hydroclimatic- fisheries model was developed. The model predicted the life-history and production parameters fairly accurately (0.53 ≤ r² ≥ 0.98, p ≤ 0.05), and showed that environmental and biological events in the floodplain significantly (0.43 ≤ r² ≥ 0.91, p ≤ 0.05) followed the periodic function of time (day-of-the-year), hence, strongly seasonal. In addition, the flood-pulse preceded all the major biological events, with predicted phase lags established at 55.6º for peak flood, 157.2º, 260.1º, 334.6º and 341.4º for condition factor for O. mossambicus, recruitment, spawning period for O. mossambicus and C. gariepinus, respectively. Therefore, it was recommended that water obstruction on the Shire River must ensure sufficient water flow during the peak flood and spawning period to allow flooding and inundation of the floodplain in order to create habitat favourable for spawning and feeding as well as improve recruitment.
- Full Text:
- Date Issued: 2005
- Authors: Chimatiro, Sloans Kalumba
- Date: 2005
- Subjects: Shire River Valley (Malawi and Mozambique) Fisheries -- Malawi
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5243 , http://hdl.handle.net/10962/d1005086
- Description: Fishes of African floodplains typically comprise populations having short life cycles, relatively few age groups, more generalised feeding behaviour, and which experience spawning success that is strongly influenced by abiotic factors such as hydrological regime of the river, climatic seasonality and habitat characteristics. In addition, African river-floodplain ecosystems do not have appropriate predictive models for estimating yield in these ecosystems. While most predictive models developed to date for floodplain fisheries have taken into account morpho-edaphic factors, they have generally excluded climatic factors as a mega-determinant of the variability of floodplain fisheries. The principle aim of this thesis has been to develop a predictive management model that incorporates data on essential biological aspects of the target species, characteristics of the habitat as well as overall climatic factors, and thus allow for adaptive management of the fisheries in a continuously fluctuating floodplain environment. Lower Shire Floodplain (34 ⁰ 45’ – 35 ⁰ E and 16 ⁰ 00’-17 ⁰ 15’ S) in Malawi, one of the major rivers-floodplains in the Zambezi Basin, was used to test this type of model. The major hypothesis tested in this study was that “the dynamics of the fishery of Lower Shire Floodplain are driven by and adapted to the seasonal, but predictable, hydro-climatic regime of the floodplain”. The specific objectives were: to describe the floodplain’s climate and hydrological pattern; to develop a quantitative characterisation of the major habitats of the Lower Shire Floodplain; to assess the fishery in terms of size, gear utilisation, gear selectivity and yield; to assess the biological parameters of the target species, necessary for the management of the fishery; to analyse how water fluctuation in the floodplain affects the recruitment and life history of the two target species; and to develop of a predictive hydro-climatic model to benefit the management of the fisheries. The climate of the floodplain was characterised by low (765 ± 198 mm) and fairly variable (Cv = 27%) rainfall, which largely occurred between December and January. The area was generally humid (mean RH 68%), with mild to hot (25- 33ºC) and variable monthly mean diurnal (12ºC) temperature. Four quarterly hydro-climatic seasons were identified and comprised: Quarter 1 (Jul-Sep) characterised by hot, dry weather with a low flood regime; Quarter 2 (Oct-Dec) hot, windy, wet weather with low-but-rising flood regime; Quarter 3 (Jan-Mar) hot humid, wet weather with the flood regime at peak; and Quarter 4 (Apr-Jun) humid and cool weather with receding flood regime. The annual hydrograph of the floodplain was represented by four categories of flood regime as: low (Jul-Sept), low-but-rising (Oct-Dec), peak (Jan- Mar), and falling (Apr-Jun). The floodplain experienced a water deficit of 95.1 mm.year⁻¹, and it was hypothesised that ground water recharge maintained water in the floodplain the rest of the year. Three major habitats were identified in the floodplain. The river-floodplain, characterised by deep fast-flowing water, sandy substrate and little emergent vegetation; the permanently connected lagoons, were shallow (≤ 2 m) with sandymud bottom and slow flowing water; and the seasonally connected lagoons had slowflowing stagnant water, with comparatively more emergent and floating vegetation. Physicochemical characteristics of the habitats varied significantly with hydroclimatic seasons (one-way ANOVA, p ≤ 0.05), indicating the influence of flood regime, which joined the habitats in a non-equilibrial spatial distribution. Consequently, during receding and low flood regimes river-floodplain and permanently connected lagoons exhibited similar characteristics while all three habitats had similar characteristics during the rising and peak flood regimes. It was, therefore, concluded that in floodplains, habitats shift horizontally and vertically according to the water level. Gill nets, cast nets, long line, and fish traps accounted for 99% of the total count of gears, and hence considered the major fishing sectors. Two principal species in the floodplain were the catfish Clarias gariepinus and the cichlid Oreochromis mossambicus. Length-at-maximum-selectivity (ø) and length-at-50%-sexual-maturity (Lm₅₀) for each of the two species showed that although they were selected into the four fishing sectors at lengths above maturity, maximum selectivity into the long line occurred at a length before maturity for O. mossambicus. In addition, the width of the gamma selectivity function (σ) indicated that a considerable proportion of juveniles of the two species were also selected. Therefore, it was decided that management for the floodplain be centred on controlling over-fishing and preserving the spawner stock, by banning seine and mosquito nets, and closing river-floodplain and permanently connected lagoons to fishing during the low flood regime. There were significant seasonal variations in CPUE, lowest in the low flood, and highest during the peak flood regime. Sectioned otoliths were used to determine the age and growth of the two principal species in the floodplain. Marginal zone analysis revealed that annulus formation in all the species occurred during the period of low air and water temperatures, high evaporation and receding water levels, hence a high rate of desiccation and negative water budget. For O. mossambicus, maximum age reached was 6 years while in C. gariepinus it was 9 years. The 3-parameter von Bertalanffy growth model adequately described growth as lt = 177.6(1-e⁻·⁴⁴⁽t ⁺ ¹·⁴³⁾) mm TL for O. mossambicus and lt = 502.9(1-e⁻°·³¹⁽t ⁺ ¹·⁹²⁾) mm TL for C. gariepinus. Female O. mossambicus reached 50%-sexual-maturity at 109 mm SL, while males matured at 105 mm, and both male and female C. gariepinus reached Lm₅₀ at 249 mm SL. The breeding seasons of both O. mossambicus and Clarias gariepinus were between September and March, with modal peaks in January and November, respectively. The annual total mortality rates (Z) were 0.62 ± 0.18 yr⁻¹ for O. mossambicus and 0.93 ± 0.47 yr⁻¹ for C. gariepinus. The mean empirical estimates of natural mortality (M) were 0.46 yr⁻¹ for O. mossambicus and 0.50 year⁻¹ for C. gariepinus, and fishing mortality (F) was calculated as 0.16 yr⁻¹ for O. mossambicus and 0.43 yr⁻¹ for C. gariepinus. The overall exploitation level (Z/K) was 1.41 for O. mossambicus and 3.01 for C. gariepinus. Given that the Z/K ratio was >1, it was asserted that both O. mossambicus and C. gariepinus were mortality-dominated and fairly heavily exploited. However, potential for sustainable exploitation existed since both species showed signs of resilience due short longevity and high rate of natural mortality. Given the limitation of simple exponential models of fish mortality and growth under the situation of seasonal fluctuation of water levels, a simple predictive hydroclimatic- fisheries model was developed. The model predicted the life-history and production parameters fairly accurately (0.53 ≤ r² ≥ 0.98, p ≤ 0.05), and showed that environmental and biological events in the floodplain significantly (0.43 ≤ r² ≥ 0.91, p ≤ 0.05) followed the periodic function of time (day-of-the-year), hence, strongly seasonal. In addition, the flood-pulse preceded all the major biological events, with predicted phase lags established at 55.6º for peak flood, 157.2º, 260.1º, 334.6º and 341.4º for condition factor for O. mossambicus, recruitment, spawning period for O. mossambicus and C. gariepinus, respectively. Therefore, it was recommended that water obstruction on the Shire River must ensure sufficient water flow during the peak flood and spawning period to allow flooding and inundation of the floodplain in order to create habitat favourable for spawning and feeding as well as improve recruitment.
- Full Text:
- Date Issued: 2005
The degradation of lignocellulose in a biologically-generated sulphidic environment
- Authors: Roman, Henry James
- Date: 2005
- Subjects: Lignocellulose Sulfides Lignin Lignocellulose -- Biodegradation Mines and mineral resources -- Waste disposal Acid mine drainage
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3997 , http://hdl.handle.net/10962/d1004057
- Description: South Africa is renowned for its mining industry. The period over which the polluted waters from the existing and abandoned mines will require treatment has driven research into the development of passive treatment systems. These waters are characterised by a low pH, high concentrations of heavy metals, high levels of sulphate salts and low concentrations of organic material. The biological treatment of these waters has been a subject of increasing focus as an alternative to physicochemical treatment. The utilisation of lignocellulose as a carbon source has been restricted by the amount of reducing equivalents available within the lignocellulose matrix. After a few months of near 100% sulphate reduction, it was found that although there was a large fraction of lignin and cellulose remaining, sulphate reduction was reduced to less than 20%. The present study demonstrated that lignocellulose can be utilised as a carbon source for sulphate reduction. It was established that lignocellulose degradation was enhanced under biosulphidogenic conditions and that lignin could be degraded by a sulphate reducing microbial consortium. It was established using lignin model compounds synthesized in our laboratory, that the bonds within the lignin polymer can be cleaved within the sulphidic environment. The presence of cellulolytic enzymes, using CMCase as a marker enzyme, was detected within the sulphate reducing microbial consortium. Based on the results obtained a descriptive model was formulated for the degradation of lignocellulose under biosulphidogenic conditions. It was determined that the initial reduction in sulphate observed using lignocellulose as a carbon source was due to the easily extractable components. The degradation of which resulted in the production of sulphide, which aided in the degradation of lignin, allowing greater access to cellulose. Once the easily extractable material is exhausted, the cycle is halted, unless the sulphide production can be maintained. This is the focus of an ongoing project, testing the hypothesis that an easy to assimilate carbon source added after exhaustion of the easily extractable material, can maintain the sulphide production.
- Full Text:
- Date Issued: 2005
- Authors: Roman, Henry James
- Date: 2005
- Subjects: Lignocellulose Sulfides Lignin Lignocellulose -- Biodegradation Mines and mineral resources -- Waste disposal Acid mine drainage
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3997 , http://hdl.handle.net/10962/d1004057
- Description: South Africa is renowned for its mining industry. The period over which the polluted waters from the existing and abandoned mines will require treatment has driven research into the development of passive treatment systems. These waters are characterised by a low pH, high concentrations of heavy metals, high levels of sulphate salts and low concentrations of organic material. The biological treatment of these waters has been a subject of increasing focus as an alternative to physicochemical treatment. The utilisation of lignocellulose as a carbon source has been restricted by the amount of reducing equivalents available within the lignocellulose matrix. After a few months of near 100% sulphate reduction, it was found that although there was a large fraction of lignin and cellulose remaining, sulphate reduction was reduced to less than 20%. The present study demonstrated that lignocellulose can be utilised as a carbon source for sulphate reduction. It was established that lignocellulose degradation was enhanced under biosulphidogenic conditions and that lignin could be degraded by a sulphate reducing microbial consortium. It was established using lignin model compounds synthesized in our laboratory, that the bonds within the lignin polymer can be cleaved within the sulphidic environment. The presence of cellulolytic enzymes, using CMCase as a marker enzyme, was detected within the sulphate reducing microbial consortium. Based on the results obtained a descriptive model was formulated for the degradation of lignocellulose under biosulphidogenic conditions. It was determined that the initial reduction in sulphate observed using lignocellulose as a carbon source was due to the easily extractable components. The degradation of which resulted in the production of sulphide, which aided in the degradation of lignin, allowing greater access to cellulose. Once the easily extractable material is exhausted, the cycle is halted, unless the sulphide production can be maintained. This is the focus of an ongoing project, testing the hypothesis that an easy to assimilate carbon source added after exhaustion of the easily extractable material, can maintain the sulphide production.
- Full Text:
- Date Issued: 2005
The design and evaluation of a short-term group psychotherapy model for survivors of a first myocardial infarction
- Authors: Frewen, Sharon H
- Date: 2005
- Subjects: Health -- Psychological aspects , Medicine and psychology , Coronary heart disease -- Psychological aspects , Type A behavior , Stress (Psychology)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3247 , http://hdl.handle.net/10962/d1015041
- Description: There is extensive evidence that the rehabilitation of individuals with coronary heart disease needs to include psychological components to complement the exercise and dietary recommendations that are normally provided. However, psychological aspects have not been integrated into medical care in South Africa to any significant degree. Psychological interventions overseas have included the modification of the Type A behaviour pattern, stress management, cognitive restructuring, relaxation techniques, improved communication skills, the identification and expression of emotions, and emotional support. The aim of the present study was to design a short-term group intervention which incorporated these aspects and which included an exploration of the mind-body experience post infarct. In addition, the intervention aimed to increase participants' awareness of the compensatory dynamics of the Type A behaviour pattern. The intervention was tailored to South African conditions and was evaluated by means of a multiple case study design. The intervention was delivered to a group of nine coronary heart disease patients which included six survivors of myocardial infarction, the remaining participants having undergone a by-pass operation. Data included weekly feedback sheets evaluating each session, repeated measures on the Profile of Mood States, the Jenkins Activity Survey, a Spouse Rating Scale and extensive qualitative data on each participant including tape recordings of each session and data collected from a series of interviews before, during and after the programme. The feedback sheets and recordings of the sessions were used as a basis for recommendations for revising the content and structure of the programme for future use. Case narratives were written for three of the participants and provided an in-depth look at how and why individual changes did or did not occur in response to the intervention. In addition, the case narratives revealed the role played by the compensatory dynamics of the Type A behaviour pattern in complicating rehabilitation for survivors of myocardial infarction. Two participants were offered a series of individual sessions at 18-month follow-up and the material from these sessions was also used to aid in the interpretation of the data. The content of the 18-month follow-up sessions provided evidence for the importance of conducting a developmental analysis of the origins of low self-esteem and insecurity that maintain and drive the Type A behaviour pattern. In these sessions, this analysis provided the basis for a brief focused psychodynamic psychotherapy that facilitated marked changes that had not been achieved in the 12-week structured group intervention. It is recommended that future research investigate the use of brief psychodynamic psychotherapy on an individual basis as a complement to a group intervention focusing on psycho-education, building social support and management of problematic emotions in everyday situations.
- Full Text:
- Date Issued: 2005
- Authors: Frewen, Sharon H
- Date: 2005
- Subjects: Health -- Psychological aspects , Medicine and psychology , Coronary heart disease -- Psychological aspects , Type A behavior , Stress (Psychology)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3247 , http://hdl.handle.net/10962/d1015041
- Description: There is extensive evidence that the rehabilitation of individuals with coronary heart disease needs to include psychological components to complement the exercise and dietary recommendations that are normally provided. However, psychological aspects have not been integrated into medical care in South Africa to any significant degree. Psychological interventions overseas have included the modification of the Type A behaviour pattern, stress management, cognitive restructuring, relaxation techniques, improved communication skills, the identification and expression of emotions, and emotional support. The aim of the present study was to design a short-term group intervention which incorporated these aspects and which included an exploration of the mind-body experience post infarct. In addition, the intervention aimed to increase participants' awareness of the compensatory dynamics of the Type A behaviour pattern. The intervention was tailored to South African conditions and was evaluated by means of a multiple case study design. The intervention was delivered to a group of nine coronary heart disease patients which included six survivors of myocardial infarction, the remaining participants having undergone a by-pass operation. Data included weekly feedback sheets evaluating each session, repeated measures on the Profile of Mood States, the Jenkins Activity Survey, a Spouse Rating Scale and extensive qualitative data on each participant including tape recordings of each session and data collected from a series of interviews before, during and after the programme. The feedback sheets and recordings of the sessions were used as a basis for recommendations for revising the content and structure of the programme for future use. Case narratives were written for three of the participants and provided an in-depth look at how and why individual changes did or did not occur in response to the intervention. In addition, the case narratives revealed the role played by the compensatory dynamics of the Type A behaviour pattern in complicating rehabilitation for survivors of myocardial infarction. Two participants were offered a series of individual sessions at 18-month follow-up and the material from these sessions was also used to aid in the interpretation of the data. The content of the 18-month follow-up sessions provided evidence for the importance of conducting a developmental analysis of the origins of low self-esteem and insecurity that maintain and drive the Type A behaviour pattern. In these sessions, this analysis provided the basis for a brief focused psychodynamic psychotherapy that facilitated marked changes that had not been achieved in the 12-week structured group intervention. It is recommended that future research investigate the use of brief psychodynamic psychotherapy on an individual basis as a complement to a group intervention focusing on psycho-education, building social support and management of problematic emotions in everyday situations.
- Full Text:
- Date Issued: 2005
The development of a cultural family business model of good governance for Greek family businesses in South Africa
- Adendorff, Christian Michael
- Authors: Adendorff, Christian Michael
- Date: 2005
- Subjects: Family-owned business enterprises -- South Africa Greeks -- South Africa Greeks -- South Africa -- Social life and customs Corporate governance -- South Africa South Africa -- Economic conditions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1163 , http://hdl.handle.net/10962/d1002779
- Description: Never in the history of the South African nation has the entrepreneurial spirit been more alive. Since the opening of international doors, after the 1994 elections, South Africa has experienced the explosive growth of transnational entrepreneurship. An enduring aspect of the explosion of such economic activity is the need for "good governance" and the need for governance education in South Africa and the rest of the continent has never been greater. The size of the family business component of the South Aftican economy suggests that it is the predominant way of doing business in South Africa. Of importance to this study is the estimate that approximately 95 % of all Greek businesses in South Africa can be classified as family businesses. The sustainability of Greek family businesses requires that they maintain good governance practices that are economically and environmentally acceptable to all stakeholders. It also requires that the next generation of Greek entrepreneurs balance good governance for the businesses as well as for the family. The primary objective of this study was to identify and explore the internal factors that influence and determine good governance to ensure the survival, growth and sustainability of Greek family businesses in South Africa. The secondary research objectives pertained to the underlying dimensions of good governance and required an exploration of the different governance concerns in relation to specific South African Greek behaviour and characteristics. A theoretical model of good governance factors was proposed and tested using Structural Equation Modeling. The study found that perceived good governance in a South African Greek family business context needs to be measured in terms of three factors, namely risk control, the internal regulatory environment and the protection of the stakeholders' interest. The study dealt further with the secondary sources effecting governance for South African businesses and was based on the latest report by the King Commission. An important finding is that the cross cultural aspect of family business governance must now be considered when conducting such research as more and more emphasis is placed on the good governance of all businesses.
- Full Text:
- Date Issued: 2005
- Authors: Adendorff, Christian Michael
- Date: 2005
- Subjects: Family-owned business enterprises -- South Africa Greeks -- South Africa Greeks -- South Africa -- Social life and customs Corporate governance -- South Africa South Africa -- Economic conditions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1163 , http://hdl.handle.net/10962/d1002779
- Description: Never in the history of the South African nation has the entrepreneurial spirit been more alive. Since the opening of international doors, after the 1994 elections, South Africa has experienced the explosive growth of transnational entrepreneurship. An enduring aspect of the explosion of such economic activity is the need for "good governance" and the need for governance education in South Africa and the rest of the continent has never been greater. The size of the family business component of the South Aftican economy suggests that it is the predominant way of doing business in South Africa. Of importance to this study is the estimate that approximately 95 % of all Greek businesses in South Africa can be classified as family businesses. The sustainability of Greek family businesses requires that they maintain good governance practices that are economically and environmentally acceptable to all stakeholders. It also requires that the next generation of Greek entrepreneurs balance good governance for the businesses as well as for the family. The primary objective of this study was to identify and explore the internal factors that influence and determine good governance to ensure the survival, growth and sustainability of Greek family businesses in South Africa. The secondary research objectives pertained to the underlying dimensions of good governance and required an exploration of the different governance concerns in relation to specific South African Greek behaviour and characteristics. A theoretical model of good governance factors was proposed and tested using Structural Equation Modeling. The study found that perceived good governance in a South African Greek family business context needs to be measured in terms of three factors, namely risk control, the internal regulatory environment and the protection of the stakeholders' interest. The study dealt further with the secondary sources effecting governance for South African businesses and was based on the latest report by the King Commission. An important finding is that the cross cultural aspect of family business governance must now be considered when conducting such research as more and more emphasis is placed on the good governance of all businesses.
- Full Text:
- Date Issued: 2005
The early proterozoic Makganyene glacial event in South Africa : its implication in sequence stratigraphy interpretations, paleoenvironmental conditions and iron and manganese ore deposition
- Authors: Polteau, Stéphane
- Date: 2005
- Subjects: Geology, Stratigraphic -- South Africa -- Northern Cape Geochemistry -- South Africa -- Northern Cape Paleogeography -- South Africa -- Northern Cape Petrology -- South Africa -- Northern Cape Ore deposits -- South Africa -- Northern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5039 , http://hdl.handle.net/10962/d1007612
- Description: The Makganyene Formation forms the base of the Postmasburg Group in the Transvaal Supergroup in the Griqualand West Basin. It consists of diamictites, sandstones, banded iron-formations (BIFs), shales, siltstones and carbonates. It is generally accepted that the Makganyene Formation rests on an erosive regional unconformity throughout the Northern Cape Province. However this study demonstrates that this stratigraphic relationship is not universal, and conformable contacts have been observed. One of the principal aims of this study is to identify the nature of the Makganyene basal contact throughout the Griqualand West Basin. Intensive fieldwork was carried out from Prieska in the south, to Danielskuil in the north. In the Sishen and Hotazel areas, only borehole material was available to assess the stratigraphy. The Griquatown Fault Zone delimits the boundary between the deep basin and platform facies. The Koegas Subgroup is only present south of the Griquatown Fault Zone, where it pinches out. However, the transition Griquatown BIFs-Koegas Subgroup occurs in lacustrine deposits on the Ghaap platform (Beukes, 1983). The Griquatown Fault Zone represents the edge of the basin, which corresponds to a hinge rather than a fault zone. The Makganyene Formation rests with a conformable contact on the Koegas Subgroup south of the Griquatown Hinge Zone, and north of it the Makganyene Formation lies unconformably on the Asbestos Hills Subgroup. The Makganyene Formation displays lateral facies changes that reflect the paleogeography of the Griqualand West Basin, and the development of ice sheets/shelves. The Ghaap platform is characterised by coarse immature sand interbedded with the diamictites. The clasts in this area contain local Asbestos Hills material and no dropstones are present. Such settings are typical of sediments that are being deposited below a grounded ice mass. At the Griquatown Hinge Zone, the sandstone lenses are smaller, and the clasts consist of chert, of which a great number are striated and faceted. In the Matsap area, the presence of dropstones is strong evidence for the presence of a floating ice shelf that released its material by basal melting. Further south, the Makganyene Formation contains stromatolitic bioherms that only form if clastic contamination is minimal and therefore the ice that transported the detritus to the basin did not extend far into open sea conditions. The base of the Hotazel Formation also contains diamictite levels. Dropstones have been identified, implying a glacial origin. The Hotazel diamictites are interbedded with hyaloclastites and BIFs. The Makganyene glacial event, therefore, was not restricted to the Makganyene Formation, but also included the Ongeluk Formation, through to the base of the Hotazel Formation. Petrographic studies of the Makganyene Formation and the base of the Hotazel Formation reveal mineral assemblages that are diagnostic of early to late diagenetic crystallisation and of low-grade metamorphism not exceeding the very low green-schist facies. The facies identified display the same sense of basin deepening, from shallow high-energy Hotazel area on the Ghaap platform, to the deep basin in the Matsap area. Whole-rock geochemical analyses reveal that the elemental composition of the Makganyene Formation is very similar to that of the Asbestos Hills BIFs, which were the most important source of clastic detritus for the Makganyene Formation. However, minor amounts of carbonates of the Campbellrand Subgroup, as well as a felsic crustal input from the Archean granitoid basement, made contributions. On the Ghaap platform, the Makganyene diamictite is enriched in iron, calcium, and magnesium, while in the deeper parts of the basin the diamictites are enriched in detrital elements, such as titanium and aluminium, which occur in the fine clay component. The Hotazel diamictite displays a distinct mafic volcanic input, related to the extrusion of the Ongeluk basaltic andesites, which was incorporated in the glacial sediments. Sequence stratigraphy is based on the recognition of contacts separating the different systems tracts that compose a depositional sequence. However, because the basal contact of the Makganyene Formation has not been properly identified in previous work, no correct model has been proposed so far. Therefore correlations between the Griqualand West and the Transvaal basins, based on lithostratigraphic similarities and extrapolations of unconformities, have to be reviewed, especially since the publication of new radiometric ages contradict all previously proposed correlations. It is proposed here that the Transvaal Supergroup in the Griqualand West Basin represents a continuous depositional event that lasted about 200 Ma. The Makganyene glacial event occurred during changing conditions in the chemistries of the atmosphere and ocean, and in the continental configuration. A Snowball Earth event has been proposed as the causative process of such paleoenvironmental changes. However, evidence presented here of less dramatic glacial conditions, with areas of ice-free waters, implies an alternative to the Snowball Earth event. The paleoenvironmental changes are thought to represent a transition from an anaerobic to aerobic atmosphere, that was responsible for the global cooling of the surface of the Earth, Such a glacial event may have aided in the large-scale precipitation of iron and manganese in areas of intense upwellings.
- Full Text:
- Date Issued: 2005
- Authors: Polteau, Stéphane
- Date: 2005
- Subjects: Geology, Stratigraphic -- South Africa -- Northern Cape Geochemistry -- South Africa -- Northern Cape Paleogeography -- South Africa -- Northern Cape Petrology -- South Africa -- Northern Cape Ore deposits -- South Africa -- Northern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5039 , http://hdl.handle.net/10962/d1007612
- Description: The Makganyene Formation forms the base of the Postmasburg Group in the Transvaal Supergroup in the Griqualand West Basin. It consists of diamictites, sandstones, banded iron-formations (BIFs), shales, siltstones and carbonates. It is generally accepted that the Makganyene Formation rests on an erosive regional unconformity throughout the Northern Cape Province. However this study demonstrates that this stratigraphic relationship is not universal, and conformable contacts have been observed. One of the principal aims of this study is to identify the nature of the Makganyene basal contact throughout the Griqualand West Basin. Intensive fieldwork was carried out from Prieska in the south, to Danielskuil in the north. In the Sishen and Hotazel areas, only borehole material was available to assess the stratigraphy. The Griquatown Fault Zone delimits the boundary between the deep basin and platform facies. The Koegas Subgroup is only present south of the Griquatown Fault Zone, where it pinches out. However, the transition Griquatown BIFs-Koegas Subgroup occurs in lacustrine deposits on the Ghaap platform (Beukes, 1983). The Griquatown Fault Zone represents the edge of the basin, which corresponds to a hinge rather than a fault zone. The Makganyene Formation rests with a conformable contact on the Koegas Subgroup south of the Griquatown Hinge Zone, and north of it the Makganyene Formation lies unconformably on the Asbestos Hills Subgroup. The Makganyene Formation displays lateral facies changes that reflect the paleogeography of the Griqualand West Basin, and the development of ice sheets/shelves. The Ghaap platform is characterised by coarse immature sand interbedded with the diamictites. The clasts in this area contain local Asbestos Hills material and no dropstones are present. Such settings are typical of sediments that are being deposited below a grounded ice mass. At the Griquatown Hinge Zone, the sandstone lenses are smaller, and the clasts consist of chert, of which a great number are striated and faceted. In the Matsap area, the presence of dropstones is strong evidence for the presence of a floating ice shelf that released its material by basal melting. Further south, the Makganyene Formation contains stromatolitic bioherms that only form if clastic contamination is minimal and therefore the ice that transported the detritus to the basin did not extend far into open sea conditions. The base of the Hotazel Formation also contains diamictite levels. Dropstones have been identified, implying a glacial origin. The Hotazel diamictites are interbedded with hyaloclastites and BIFs. The Makganyene glacial event, therefore, was not restricted to the Makganyene Formation, but also included the Ongeluk Formation, through to the base of the Hotazel Formation. Petrographic studies of the Makganyene Formation and the base of the Hotazel Formation reveal mineral assemblages that are diagnostic of early to late diagenetic crystallisation and of low-grade metamorphism not exceeding the very low green-schist facies. The facies identified display the same sense of basin deepening, from shallow high-energy Hotazel area on the Ghaap platform, to the deep basin in the Matsap area. Whole-rock geochemical analyses reveal that the elemental composition of the Makganyene Formation is very similar to that of the Asbestos Hills BIFs, which were the most important source of clastic detritus for the Makganyene Formation. However, minor amounts of carbonates of the Campbellrand Subgroup, as well as a felsic crustal input from the Archean granitoid basement, made contributions. On the Ghaap platform, the Makganyene diamictite is enriched in iron, calcium, and magnesium, while in the deeper parts of the basin the diamictites are enriched in detrital elements, such as titanium and aluminium, which occur in the fine clay component. The Hotazel diamictite displays a distinct mafic volcanic input, related to the extrusion of the Ongeluk basaltic andesites, which was incorporated in the glacial sediments. Sequence stratigraphy is based on the recognition of contacts separating the different systems tracts that compose a depositional sequence. However, because the basal contact of the Makganyene Formation has not been properly identified in previous work, no correct model has been proposed so far. Therefore correlations between the Griqualand West and the Transvaal basins, based on lithostratigraphic similarities and extrapolations of unconformities, have to be reviewed, especially since the publication of new radiometric ages contradict all previously proposed correlations. It is proposed here that the Transvaal Supergroup in the Griqualand West Basin represents a continuous depositional event that lasted about 200 Ma. The Makganyene glacial event occurred during changing conditions in the chemistries of the atmosphere and ocean, and in the continental configuration. A Snowball Earth event has been proposed as the causative process of such paleoenvironmental changes. However, evidence presented here of less dramatic glacial conditions, with areas of ice-free waters, implies an alternative to the Snowball Earth event. The paleoenvironmental changes are thought to represent a transition from an anaerobic to aerobic atmosphere, that was responsible for the global cooling of the surface of the Earth, Such a glacial event may have aided in the large-scale precipitation of iron and manganese in areas of intense upwellings.
- Full Text:
- Date Issued: 2005
The life history patterns of the polychaete, Terebrasabella heterouncinata, a pest of cultured abalone
- Authors: Simon, Carol Anne
- Date: 2005
- Subjects: Polychaeta -- Physiology Sabellidae -- Physiology Abalones -- Diseases Polychaeta -- Reproduction Sabellidae -- Reproduction Abalone culture -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5336 , http://hdl.handle.net/10962/d1005632
- Description: Terebrasabella heterouncinata is a small K-selected sabellid polychaete. It is a simultaneous hermaphrodite with a semi-continuous mode of reproduction, producing relatively few large eggs that are brooded within the parental burrow until the larvae emerge, to settle on the growing edge of the abalone shell. Despite its low fecundity, this worm has become problematic on abalone farms in South Africa. The present study was conducted to gain an understanding of the life history patterns of T. helerouncinata to determine how they contributed to the success of these worms under altered conditions. This study demonstrated that conditions prevalent on abalone farms were conducive to enhancing the reproductive success of this worm, and suggests that larger, more fecund worms may have been selected for in the decade that these worms have been present on the farms. Increased nutrient availability, and possibly the increased stability of the farm environment relative to its natural environment, has led to a 1.5-fold increase in the average size of the worms. Body size was found to be positively correlated with brood size, and this resulted in worms on farms brooding 3 to 4.5 times more offspring at a time than worms from wild abalone. The ability to increase the number of eggs produced at a time may have been limited by the fact that these worms have only two ovaries. Thus, the increase in fecundity may have been related primarily to the increase in the rate at which the eggs were laid by the worms on the farms, and the increase in the coelomic space available for the storage of these rapidly developing eggs. The ability to increase the rate at which oocytes develop may be related to the vitellogenic mechanisms employed by these worms. Vitellogenic oocytes are able to incorporate high molecular weight yolk precursors from the surrounding coelomic fluid through endocytotic activity. This may allow the oocytes to increase the rate at which they incorporate yolk material under conditions of nutrient enrichment. The increase in fecundity did not occur at the expense of offspring size and, presumably, quality. The increased reproductive output on the farms was compounded by a proportionate increase in the number of reproducing worms within the population. In addition, these worms are long-lived (worms from farmed abalone reached a maximum age of approximately 40 months) and exhibit negligible senescence. Thus, their reproductive output did not change significantly with an increase in age. Furthermore, the proportion of the reproductive worms did not decrease with an increase in age. Thus, within the age range tested, worms of all ages have the potential to make equal contributions to population growth. While diet and abalone stocking density could not be identified as having a significant effect on reproductive output and infestation rate under intensive culture conditions, it was demonstrated that in a naïve abalone population, the total intensity of infestation increased exponentially with time. This increase may be a consequence of an increase in fertilisation success. These worms continuously produce entaquasperm that are released into the water column. The sperm are collected by other individuals that then store the sperm in a single spermatheca. The ability to store sperm relieves individuals of a dependence on the synchronisation of spawning of eggs and sperm. As the population size and density increases, there could be more individuals releasing sperm into the water column, resulting in a continuous supply of sperm. The increased production of eggs would therefore not be constrained by a lack of sperm. The stored sperm are released into the brood chamber to fertilise eggs as they are laid, and this would probably increase the fertilisation success in the species. This study also provides evidence to suggest that reproduction in this worm has a seasonal component. Future studies should concentrate on measuring fertilisation success in greater detail, measuring the effect of season on reproduction, determining whether there are genetic differences between worms on farmed and wild abalone and determining whether wild worms have similar life-spans and age-related fecundity as worms on farms.
- Full Text:
- Date Issued: 2005
- Authors: Simon, Carol Anne
- Date: 2005
- Subjects: Polychaeta -- Physiology Sabellidae -- Physiology Abalones -- Diseases Polychaeta -- Reproduction Sabellidae -- Reproduction Abalone culture -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5336 , http://hdl.handle.net/10962/d1005632
- Description: Terebrasabella heterouncinata is a small K-selected sabellid polychaete. It is a simultaneous hermaphrodite with a semi-continuous mode of reproduction, producing relatively few large eggs that are brooded within the parental burrow until the larvae emerge, to settle on the growing edge of the abalone shell. Despite its low fecundity, this worm has become problematic on abalone farms in South Africa. The present study was conducted to gain an understanding of the life history patterns of T. helerouncinata to determine how they contributed to the success of these worms under altered conditions. This study demonstrated that conditions prevalent on abalone farms were conducive to enhancing the reproductive success of this worm, and suggests that larger, more fecund worms may have been selected for in the decade that these worms have been present on the farms. Increased nutrient availability, and possibly the increased stability of the farm environment relative to its natural environment, has led to a 1.5-fold increase in the average size of the worms. Body size was found to be positively correlated with brood size, and this resulted in worms on farms brooding 3 to 4.5 times more offspring at a time than worms from wild abalone. The ability to increase the number of eggs produced at a time may have been limited by the fact that these worms have only two ovaries. Thus, the increase in fecundity may have been related primarily to the increase in the rate at which the eggs were laid by the worms on the farms, and the increase in the coelomic space available for the storage of these rapidly developing eggs. The ability to increase the rate at which oocytes develop may be related to the vitellogenic mechanisms employed by these worms. Vitellogenic oocytes are able to incorporate high molecular weight yolk precursors from the surrounding coelomic fluid through endocytotic activity. This may allow the oocytes to increase the rate at which they incorporate yolk material under conditions of nutrient enrichment. The increase in fecundity did not occur at the expense of offspring size and, presumably, quality. The increased reproductive output on the farms was compounded by a proportionate increase in the number of reproducing worms within the population. In addition, these worms are long-lived (worms from farmed abalone reached a maximum age of approximately 40 months) and exhibit negligible senescence. Thus, their reproductive output did not change significantly with an increase in age. Furthermore, the proportion of the reproductive worms did not decrease with an increase in age. Thus, within the age range tested, worms of all ages have the potential to make equal contributions to population growth. While diet and abalone stocking density could not be identified as having a significant effect on reproductive output and infestation rate under intensive culture conditions, it was demonstrated that in a naïve abalone population, the total intensity of infestation increased exponentially with time. This increase may be a consequence of an increase in fertilisation success. These worms continuously produce entaquasperm that are released into the water column. The sperm are collected by other individuals that then store the sperm in a single spermatheca. The ability to store sperm relieves individuals of a dependence on the synchronisation of spawning of eggs and sperm. As the population size and density increases, there could be more individuals releasing sperm into the water column, resulting in a continuous supply of sperm. The increased production of eggs would therefore not be constrained by a lack of sperm. The stored sperm are released into the brood chamber to fertilise eggs as they are laid, and this would probably increase the fertilisation success in the species. This study also provides evidence to suggest that reproduction in this worm has a seasonal component. Future studies should concentrate on measuring fertilisation success in greater detail, measuring the effect of season on reproduction, determining whether there are genetic differences between worms on farmed and wild abalone and determining whether wild worms have similar life-spans and age-related fecundity as worms on farms.
- Full Text:
- Date Issued: 2005
The nature and potential of industrial development within the Southern African Development Community (SADC) and the facilitating role of trade liberalisation and foreign direct investment in selected countries
- Authors: Mutambara, Tsitsi Effie
- Date: 2005
- Subjects: Southern African Development Community Investments, Foreign -- Africa, Southern Free trade -- Africa, Southern Economic development -- Africa, Southern Industrialization -- Africa, Southern Industrial policy -- Africa, Southern Africa, Southern -- Economic policy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1071 , http://hdl.handle.net/10962/d1007732
- Description: To date the SADC region has managed to develop a manufacturing base but this base is still small as evidenced by its low contribution to GDP. For example, only three out of the fourteen SADC countries, viz. Mauritius, South Africa and Swaziland, had over 20 percent of their GDP originating from the manufacturing sector throughout the 1990s. Also to note is that while the manufacturing sector is quite diversified, the sector is dominated by industrial processes which are more of resource and labour-intensive in nature than those processes of scale-intensive, differentiated and science based in nature. TIle trade performance of the manufacturing sector supports these observations and as such the region is heavily dependent on imports for scale-intensive, differentiated and science based commodities. However, despite the fact that the region tends to focus more on resource- and labour-intensive manufacturing activities, products from these manufacturing activities are still significant components of manufactured goods imports into the region. Also to note is that since resource- and labour-intensive industries dominate manufacturing activities; these are the areas in which investment opportunities abound. For example, agro-based manufacturing presents most of the investment opportunities, with food processing presenting the majority of the investment opportunities followed by garments and textiles production. Mineral processing also presents significant investment opportunities. The analyses of the nature of the manufacturing sector also show that in a few SADC countries, viz. Mauritius, South Africa and Zimbabwe; scale-intensive, differentiated and science based industries also form a significant component of the industrial base implying more technologically complex manufacturing sectors. Since high technology and technologically complex manufacturing activities are limited, investment opportunities in these manufacturing sub-sectors are also limited to just a few countries However, with the SADC ITA in place, opportunities could arise for these limited technology-related manufacturing facilities to expand or engage in import substitution production so as to meet the demands of the growing regional market. It is also important to note that, while the region may not have as competitive advantage in these industries as in the resource- and labour-intensive industries, there is a need for the region to selectively identify and target such industries for priority development, a lesson SADC could learn from the East Asian NIC's took in their industrialisation strategy. The study also shows that the manufacturing sector has been a priority sector for both domestic and foreign investors. This has implications for industrial development because a strong and dynamic manufacturing sector would be developed, forming a sound basis for industrialisation as well as being able to effectively link and support all the other sectors of the economy. FDI could help the region to fully utilise the labour-intensive industries and use them as a stepping-stone to higher levels of industrial development. This is a lesson to SADC from the experiences of the East Asian NICs where while industrialisation was initiated by labour-intensive manufacturing, the countries were able to move into capital-intensive manufacturing due to FDI as it enabled the establishment of the industrial bases, thus leading to a rise in the share of manufactured exports. FDI could also help to develop the resource-intensive industries further by promoting further processing of raw materials into products of more value, thus propelling industrialisation through a resource-led industrial development programme as the current resource-intensive industries become fully utilised. The raw materials which occur in great abundance in the region's primary sector would have a ready market in the manufacturing sector where they would serve as inputs to the production of high value products. The currently smaller industrial base for scale-intensive products, differentiated and science-based manufactured products would benefit from the improved technological capabilities and managerial skills that result from FDI. Therefore, by impacting positively on manufacturing activities of both low and high MVA, FDI would thus have a facilitating role in establishing a more solid industrial base, broadening the current manufacturing base, and improving installed capacity utilisation. The study also shows that investment in productive capacity in the form of machinery and equipment is of great importance in the sampled SADC countries. Investment towards the acquisition of this capital is very important as this is directly relevant towards improving productive capacity. FDI could thus play a facilitating role by augmenting the current domestic investment in machinery and equipment. While the manufacturing sector within the region is still small and the current utilisation of installed industrial capacity is low, there is potential for further industrial growth. The current process to usher in the SADC Free Trade Area would have a facilitating role through various ways: viz. increasing the market size and enabling easier access through the reduction of tariff and non-tariff barriers, promoting regional competitiveness, improved utilisation of regional corridors, increasing opportunities for utilising identified intra-industry trade potentials, and providing opportunities for increased regional cross-border investment. Apart from the SADC FTA, the USA African Growth and Opportunity Act (AGOA) and the Cotonou Agreement will also motivate the identification and utilisation of existing and new potentials within the manufacturing sector in SADC. In order to improve the current nature of industries in the region, there is also a need to design and implement appropriate industrial policies and strategies. Such policies should consider the region's trade policies and the recently launched Regional Indicative Strategic Development Plan (RISDP) so as to complement them. The industrial policies should also address issues relating to industrial investment, technology and local technological capabilities development, human resources development, the structure and nature of industry, the competitiveness of industries, as well as facilitating the complementarities between the agricultural and manufacturing sectors. To this end therefore, instead of relying solely on individual national industrial policies, SADC is in the process of formulating a regional industrial policy and strategies which seek to promote and support sustainable industrial growth across the region, thus facilitating industrial development.
- Full Text:
- Date Issued: 2005
- Authors: Mutambara, Tsitsi Effie
- Date: 2005
- Subjects: Southern African Development Community Investments, Foreign -- Africa, Southern Free trade -- Africa, Southern Economic development -- Africa, Southern Industrialization -- Africa, Southern Industrial policy -- Africa, Southern Africa, Southern -- Economic policy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1071 , http://hdl.handle.net/10962/d1007732
- Description: To date the SADC region has managed to develop a manufacturing base but this base is still small as evidenced by its low contribution to GDP. For example, only three out of the fourteen SADC countries, viz. Mauritius, South Africa and Swaziland, had over 20 percent of their GDP originating from the manufacturing sector throughout the 1990s. Also to note is that while the manufacturing sector is quite diversified, the sector is dominated by industrial processes which are more of resource and labour-intensive in nature than those processes of scale-intensive, differentiated and science based in nature. TIle trade performance of the manufacturing sector supports these observations and as such the region is heavily dependent on imports for scale-intensive, differentiated and science based commodities. However, despite the fact that the region tends to focus more on resource- and labour-intensive manufacturing activities, products from these manufacturing activities are still significant components of manufactured goods imports into the region. Also to note is that since resource- and labour-intensive industries dominate manufacturing activities; these are the areas in which investment opportunities abound. For example, agro-based manufacturing presents most of the investment opportunities, with food processing presenting the majority of the investment opportunities followed by garments and textiles production. Mineral processing also presents significant investment opportunities. The analyses of the nature of the manufacturing sector also show that in a few SADC countries, viz. Mauritius, South Africa and Zimbabwe; scale-intensive, differentiated and science based industries also form a significant component of the industrial base implying more technologically complex manufacturing sectors. Since high technology and technologically complex manufacturing activities are limited, investment opportunities in these manufacturing sub-sectors are also limited to just a few countries However, with the SADC ITA in place, opportunities could arise for these limited technology-related manufacturing facilities to expand or engage in import substitution production so as to meet the demands of the growing regional market. It is also important to note that, while the region may not have as competitive advantage in these industries as in the resource- and labour-intensive industries, there is a need for the region to selectively identify and target such industries for priority development, a lesson SADC could learn from the East Asian NIC's took in their industrialisation strategy. The study also shows that the manufacturing sector has been a priority sector for both domestic and foreign investors. This has implications for industrial development because a strong and dynamic manufacturing sector would be developed, forming a sound basis for industrialisation as well as being able to effectively link and support all the other sectors of the economy. FDI could help the region to fully utilise the labour-intensive industries and use them as a stepping-stone to higher levels of industrial development. This is a lesson to SADC from the experiences of the East Asian NICs where while industrialisation was initiated by labour-intensive manufacturing, the countries were able to move into capital-intensive manufacturing due to FDI as it enabled the establishment of the industrial bases, thus leading to a rise in the share of manufactured exports. FDI could also help to develop the resource-intensive industries further by promoting further processing of raw materials into products of more value, thus propelling industrialisation through a resource-led industrial development programme as the current resource-intensive industries become fully utilised. The raw materials which occur in great abundance in the region's primary sector would have a ready market in the manufacturing sector where they would serve as inputs to the production of high value products. The currently smaller industrial base for scale-intensive products, differentiated and science-based manufactured products would benefit from the improved technological capabilities and managerial skills that result from FDI. Therefore, by impacting positively on manufacturing activities of both low and high MVA, FDI would thus have a facilitating role in establishing a more solid industrial base, broadening the current manufacturing base, and improving installed capacity utilisation. The study also shows that investment in productive capacity in the form of machinery and equipment is of great importance in the sampled SADC countries. Investment towards the acquisition of this capital is very important as this is directly relevant towards improving productive capacity. FDI could thus play a facilitating role by augmenting the current domestic investment in machinery and equipment. While the manufacturing sector within the region is still small and the current utilisation of installed industrial capacity is low, there is potential for further industrial growth. The current process to usher in the SADC Free Trade Area would have a facilitating role through various ways: viz. increasing the market size and enabling easier access through the reduction of tariff and non-tariff barriers, promoting regional competitiveness, improved utilisation of regional corridors, increasing opportunities for utilising identified intra-industry trade potentials, and providing opportunities for increased regional cross-border investment. Apart from the SADC FTA, the USA African Growth and Opportunity Act (AGOA) and the Cotonou Agreement will also motivate the identification and utilisation of existing and new potentials within the manufacturing sector in SADC. In order to improve the current nature of industries in the region, there is also a need to design and implement appropriate industrial policies and strategies. Such policies should consider the region's trade policies and the recently launched Regional Indicative Strategic Development Plan (RISDP) so as to complement them. The industrial policies should also address issues relating to industrial investment, technology and local technological capabilities development, human resources development, the structure and nature of industry, the competitiveness of industries, as well as facilitating the complementarities between the agricultural and manufacturing sectors. To this end therefore, instead of relying solely on individual national industrial policies, SADC is in the process of formulating a regional industrial policy and strategies which seek to promote and support sustainable industrial growth across the region, thus facilitating industrial development.
- Full Text:
- Date Issued: 2005
The status and natural history of pygmy (Kogia breviceps) and dwarf (K. sima) sperm whales off Southern Africa
- Authors: Plön, Stephanie
- Date: 2005
- Subjects: Pygmy sperm whale Dwarf sperm whale Population genetics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5772 , http://hdl.handle.net/10962/d1005460
- Description: For the present study 106 strandings of Kogia breviceps and 85 strandings of K. sima along the South African coastline between 1880 and 1995 were analysed in order to examine the age and growth, male and female reproduction, diet, stranding patterns, and population genetic structure of both species. Length and weight at birth were about 120cm and 53kg for K. breviceps and about 103cm and 14kg for K. sima. Von Bertalanffy growth curves were fitted to the data and indicated that physical maturity was reached at around 15 years in both sexes of K. breviceps and at 13 years in female and 15 years in male K. sima. Asymptotic length was reached at 306.0 and 286.1cm in female and male K. breviceps and 249.14 and 263.75cm in female and male K. sima, respectively. Maximum ages were16 years for male K. breviceps and 23 years for females and 17 years for male K. sima and 22 years for females. Reversed sexual size dimorphism was suggested for K. breviceps, while in K. sima males were larger than females. Attainment of sexual maturity in males occurred at between 2.5 and 5 years of age in K. breviceps and 2.6 and 3 years in K. sima, corresponding to 241-242cm and 197cm body length, respectively. The maximum combined testis weight comprised 1.04% and 2.00% for K. breviceps and K. sima, respectively, and a polygynous mating system with a roving male strategy was proposed for both species. The sperm morphology for both Kogia species was described and is characterised by 20-25 spherical mitochondria arranged in rows around the midpiece. Attainment of sexual maturity in females occurred at 5 years in both Kogia species, and at 262cm and 215cm body length in K. breviceps and K. sima, respectively. The ovulation rates were 0.9 and 0.7 per year for K. breviceps and K. sima, respectively. In K. breviceps conceptions occurred from April to September and births from March to August, while in K. sima both conceptions and births occurred from December to March. Annual reproduction and a post-partum oestrus was suggested for both Kogia species. The diet of K. breviceps comprised 50 different cephalopod species from 22 families and 17 other prey species, while K. sima fed on 32 cephalopod species from 17 families and six others. Although niche overlap indices between the two species and between groups within each species were high, some differences in diet could be determined, which allow these two sympatrically occurring species to share the same ecological niche off the coast of Southern Africa. An analysis of the stranding patterns revealed that K. sima has a closer affinity to the Agulhas current and to higher water temperatures than K. breviceps, which is supported by differences in the size of the appendages between the two species. The population genetic analysis revealed a high haplotype and nucleotide diversity for K. breviceps in the Southern hemisphere, but a lack of significant phylogeographic structure, indicating substantial gene flow among populations and inhibiting genetic differentiation of local populations, although the South African population was somewhat isolated from others in the Southern Hemisphere. In contrast the data on the phylogeographic structure of K. sima were somewhat restrictive as the majority of the samples originated from South Africa. Nevertheless, both nucleotide and haplotype diversities were markedly lower than in K. breviceps and more similar to those for other small cetacean populations, suggesting a smaller population size for K. sima than for K. breviceps. Although both Kogia species belong to the medium to larger-sized odontocetes their life histories are located near the fast end of the slow-fast continuum of life histories of marine mammals, indicating high mortality rates. The “false-gill” marking and the ability to squirt ink are thought to reflect adaptations to predator mimicry and avoidance.
- Full Text:
- Date Issued: 2005
- Authors: Plön, Stephanie
- Date: 2005
- Subjects: Pygmy sperm whale Dwarf sperm whale Population genetics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5772 , http://hdl.handle.net/10962/d1005460
- Description: For the present study 106 strandings of Kogia breviceps and 85 strandings of K. sima along the South African coastline between 1880 and 1995 were analysed in order to examine the age and growth, male and female reproduction, diet, stranding patterns, and population genetic structure of both species. Length and weight at birth were about 120cm and 53kg for K. breviceps and about 103cm and 14kg for K. sima. Von Bertalanffy growth curves were fitted to the data and indicated that physical maturity was reached at around 15 years in both sexes of K. breviceps and at 13 years in female and 15 years in male K. sima. Asymptotic length was reached at 306.0 and 286.1cm in female and male K. breviceps and 249.14 and 263.75cm in female and male K. sima, respectively. Maximum ages were16 years for male K. breviceps and 23 years for females and 17 years for male K. sima and 22 years for females. Reversed sexual size dimorphism was suggested for K. breviceps, while in K. sima males were larger than females. Attainment of sexual maturity in males occurred at between 2.5 and 5 years of age in K. breviceps and 2.6 and 3 years in K. sima, corresponding to 241-242cm and 197cm body length, respectively. The maximum combined testis weight comprised 1.04% and 2.00% for K. breviceps and K. sima, respectively, and a polygynous mating system with a roving male strategy was proposed for both species. The sperm morphology for both Kogia species was described and is characterised by 20-25 spherical mitochondria arranged in rows around the midpiece. Attainment of sexual maturity in females occurred at 5 years in both Kogia species, and at 262cm and 215cm body length in K. breviceps and K. sima, respectively. The ovulation rates were 0.9 and 0.7 per year for K. breviceps and K. sima, respectively. In K. breviceps conceptions occurred from April to September and births from March to August, while in K. sima both conceptions and births occurred from December to March. Annual reproduction and a post-partum oestrus was suggested for both Kogia species. The diet of K. breviceps comprised 50 different cephalopod species from 22 families and 17 other prey species, while K. sima fed on 32 cephalopod species from 17 families and six others. Although niche overlap indices between the two species and between groups within each species were high, some differences in diet could be determined, which allow these two sympatrically occurring species to share the same ecological niche off the coast of Southern Africa. An analysis of the stranding patterns revealed that K. sima has a closer affinity to the Agulhas current and to higher water temperatures than K. breviceps, which is supported by differences in the size of the appendages between the two species. The population genetic analysis revealed a high haplotype and nucleotide diversity for K. breviceps in the Southern hemisphere, but a lack of significant phylogeographic structure, indicating substantial gene flow among populations and inhibiting genetic differentiation of local populations, although the South African population was somewhat isolated from others in the Southern Hemisphere. In contrast the data on the phylogeographic structure of K. sima were somewhat restrictive as the majority of the samples originated from South Africa. Nevertheless, both nucleotide and haplotype diversities were markedly lower than in K. breviceps and more similar to those for other small cetacean populations, suggesting a smaller population size for K. sima than for K. breviceps. Although both Kogia species belong to the medium to larger-sized odontocetes their life histories are located near the fast end of the slow-fast continuum of life histories of marine mammals, indicating high mortality rates. The “false-gill” marking and the ability to squirt ink are thought to reflect adaptations to predator mimicry and avoidance.
- Full Text:
- Date Issued: 2005
The therapist as a "bad object": the use of countertransference enactment to facilitate communication in therapy
- Authors: Webster, Penny
- Date: 2005
- Subjects: Countertransference (Psychology) Countertransference (Psychology) -- Therapeutic use Communication -- Psychological aspects Psychotherapist and patient Psychoanalysis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3083 , http://hdl.handle.net/10962/d1002592
- Description: Psychoanalysis as it exists today is not constituted by a single theoretical framework describing pathology and indicating a specific set of interventions. Since Freud originally conceptualised psychoanalytic understanding of pathology and psychoanalysis as a mode of intervention, there have been many revisions and reformulations of his theory. This thesis has attempted to integrate some psychoanalytic ideas regarding personality formation, psychopathology and psychotherapeutic intervention (Fairbairn, 1952; Ogden, 1992, 1994), with interpersonal (strategic / structural) ideas regarding intervention (Minuchin, 1974; Sullivan, 1940, 1953, 1964). In order to do so, the thesis used the relational psychoanalytic perspective, as depicted by Aron (1996) and Mitchell and Aron (1999), as an overarching conceptual framework. The focus from these points of view is the patient's internalized relationship patterns and the therapist's participation in their repetition. It is held that internalized relationship patterns are not only based on, but can be changed by, lived experience. From this perspective, the goal of therapy is to enhance the patient's capacity to reflect and think about experience, and therefore, to communicate about it. This means a change in the patient's predominant mode of communication. Ogden's (1994) modes of communication were described. The thesis suggested that Ogden's modes of communication can be stretched or translated into the types of communication outlined by Langs (1978). This thesis aimed to explore the deliberate use of countertransference responses to facilitate communication in the beginning stages of therapy with patients functioning predominantly in the paranoid-schizoid mode (Ogden, 1992). Patients who operate in this mode are often unable to tolerate interpretation and therefore traditional approaches to intervention are not effective. A "strategic / structural relational psychoanalytic" approach to treatment was proposed. It was suggested that therapists utilize joining and accommodation techniques as described by Minuchin (1974) and alter their style of interaction to match that of the various object relational constellations that they have managed to identify within the patient via their countertransference responses. It was hypothesized that patients need their therapists to be similar to their original objects in order to feel safe in the therapeutic environment and that this may facilitate communication in the beginning stages of therapy. The research utilized a qualitative research approach. Qualitative research methods attempt to use data gathered phenomenologically, always acknowledging the researcher's biases when gathering the data. The data gathered is then interpreted according to various theories or hermeneutic lenses. The hypothesis mentioned above has been investigated by analyzing three cases in terms of the research questions based on Langs' (1978) classification of communication. The thesis described the difficulties inherent in collecting clinical data from psychologists working from within a psychoanalytic framework. Eventually three sets of therapy details and verbatim therapy transcripts were obtained, provided in the thesis and analyzed in terms of the research questions. However evidence for the success of the hypothesized alternate approach was not found in this research study. It was suggested that other possible methods might be useful to investigate the hypothesized approach further.
- Full Text:
- Date Issued: 2005
- Authors: Webster, Penny
- Date: 2005
- Subjects: Countertransference (Psychology) Countertransference (Psychology) -- Therapeutic use Communication -- Psychological aspects Psychotherapist and patient Psychoanalysis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3083 , http://hdl.handle.net/10962/d1002592
- Description: Psychoanalysis as it exists today is not constituted by a single theoretical framework describing pathology and indicating a specific set of interventions. Since Freud originally conceptualised psychoanalytic understanding of pathology and psychoanalysis as a mode of intervention, there have been many revisions and reformulations of his theory. This thesis has attempted to integrate some psychoanalytic ideas regarding personality formation, psychopathology and psychotherapeutic intervention (Fairbairn, 1952; Ogden, 1992, 1994), with interpersonal (strategic / structural) ideas regarding intervention (Minuchin, 1974; Sullivan, 1940, 1953, 1964). In order to do so, the thesis used the relational psychoanalytic perspective, as depicted by Aron (1996) and Mitchell and Aron (1999), as an overarching conceptual framework. The focus from these points of view is the patient's internalized relationship patterns and the therapist's participation in their repetition. It is held that internalized relationship patterns are not only based on, but can be changed by, lived experience. From this perspective, the goal of therapy is to enhance the patient's capacity to reflect and think about experience, and therefore, to communicate about it. This means a change in the patient's predominant mode of communication. Ogden's (1994) modes of communication were described. The thesis suggested that Ogden's modes of communication can be stretched or translated into the types of communication outlined by Langs (1978). This thesis aimed to explore the deliberate use of countertransference responses to facilitate communication in the beginning stages of therapy with patients functioning predominantly in the paranoid-schizoid mode (Ogden, 1992). Patients who operate in this mode are often unable to tolerate interpretation and therefore traditional approaches to intervention are not effective. A "strategic / structural relational psychoanalytic" approach to treatment was proposed. It was suggested that therapists utilize joining and accommodation techniques as described by Minuchin (1974) and alter their style of interaction to match that of the various object relational constellations that they have managed to identify within the patient via their countertransference responses. It was hypothesized that patients need their therapists to be similar to their original objects in order to feel safe in the therapeutic environment and that this may facilitate communication in the beginning stages of therapy. The research utilized a qualitative research approach. Qualitative research methods attempt to use data gathered phenomenologically, always acknowledging the researcher's biases when gathering the data. The data gathered is then interpreted according to various theories or hermeneutic lenses. The hypothesis mentioned above has been investigated by analyzing three cases in terms of the research questions based on Langs' (1978) classification of communication. The thesis described the difficulties inherent in collecting clinical data from psychologists working from within a psychoanalytic framework. Eventually three sets of therapy details and verbatim therapy transcripts were obtained, provided in the thesis and analyzed in terms of the research questions. However evidence for the success of the hypothesized alternate approach was not found in this research study. It was suggested that other possible methods might be useful to investigate the hypothesized approach further.
- Full Text:
- Date Issued: 2005
Towards the development of a protocol for the selection of probiotics in marine fish larviculture
- Authors: Vine, Niall Gordon
- Date: 2005
- Subjects: Marine fishes -- Larvae Bacteria Fishes -- Microbiology Fish culture
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5329 , http://hdl.handle.net/10962/d1005175
- Description: Manipulation or control of the microbiological aquaculture environment has been identified as an important focus area for future hatchery development. Subsequently, alternatives to obtain control of the microbiological environment are being sought of which the field of probiotics appears highly promising. Probiotics are usually selected based on various in vitro characteristics, however, the methods used differ and are sometimes unsuccessful due to poor experimentation. The aim of this work is to contribute towards the development of a protocol for the in vitro screening of bacterial candidate probiotics for marine fish larviculture. To reduce the number of candidate probiotics to be tested in vivo, various in vitro experiments need to be conducted, each screening for a particular mode of action – antagonism towards pathogen through production of antimicrobial compounds, growth and attachment to fish intestinal mucus, and the production of other beneficial compounds such as vitamins, fatty-acids and digestive enzymes. A total of 108 bacteria species were isolated from the digestive tract of the adult common clownfish, Amphiprion percula to screen for potential probiotics to be used in clownfish larval rearing. The antagonistic compounds assay identified twelve isolates which showed antagonism towards two or more aquatic pathogens. This was followed by an in vitro test that involved growing the organisms in fish intestinal mucus and modeling their growth parameters. A ranking index (RI) was developed using the lag period (λ) and doubling time (td) of the organism, where (1over λ x td) x 100. Five candidate probionts (AP1-AP5) with varied growth parameters were used for further in vitro experiments. The attachment to mucus assay introduced a novel tool for quantifying competition for attachment sites between candidate probionts and pathogens on mucus. Candidate probiont Pseudoalteromonas AP5 reduced the attachment ability of Vibrio alginolyticus when added before the pathogen and partially out-competed the pathogen for attachment sites when added second. In vitro screening for the production of beneficial compounds tested the candidate probiotics’ ability to produce digestive enzymes - trypsin, lipase and alkaline phosphatase as well as carotenoids and vitamin C. Candidate probiont Pseudoalteromonas AP5 produced high levels of the enzymes (98.2, 34.1 and 91.3 mU product liberated.ml⁻¹, respectively) and contained carotenoids while Kocuria AP4 contained carotenoids but produced low quantities of enzymes (7.8, 0 and 59 mU product liberated.ml⁻¹, respectively). None of the candidate probiotics produced vitamin C. To eliminate potential pathogenic or toxic candidate probionts, Artemia nauplii were exposed to each candidate probiont and the percentage Artemia mortality after 24-hours was determined. Candidate probiont AP2 caused high mortality of Artemia nauplii (98.4%) and was excluded from further studies. Identification of candidate probionts AP3-AP5 was performed using 16S-rDNA molecular techniques and the bacteria were assigned the names Bacillus AP3, Kocuria AP4 and Pseudoalteromonas AP5, respectively. Two methods of larval probiont delivery were tested – attachment to Artemia, and in-water delivery. Attachment to Artemia was high for both Kocuria AP4 and Pseudoalteromonas AP5 (7.2 x10³ and 2.7x10⁴ bacteria.nauplius⁻¹, respectively) while the in-water viability experiment showed that Kocuria AP4 comprised 23.9% of the total culturable water microflora after 24 hours while Pseudoalteromonas AP5 contributed 100%. To validate the findings from the in vitro experiments, in vivo trials using clownfish larvae were performed. Of the four candidate probiotics tested, only Kocuria AP4 showed potential to increase larval survival. In vitro tests produced a better understanding of the possible mode of action and strategies of competition between bacteria, however, the number of criteria in which a candidate probiont is successful in vitro may not be the best predictor for its effectiveness in vivo. Commercial studies that reduce between-treatment variation are required to test predictions about the most suitable probiont or combinations thereof.
- Full Text:
- Date Issued: 2005
- Authors: Vine, Niall Gordon
- Date: 2005
- Subjects: Marine fishes -- Larvae Bacteria Fishes -- Microbiology Fish culture
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5329 , http://hdl.handle.net/10962/d1005175
- Description: Manipulation or control of the microbiological aquaculture environment has been identified as an important focus area for future hatchery development. Subsequently, alternatives to obtain control of the microbiological environment are being sought of which the field of probiotics appears highly promising. Probiotics are usually selected based on various in vitro characteristics, however, the methods used differ and are sometimes unsuccessful due to poor experimentation. The aim of this work is to contribute towards the development of a protocol for the in vitro screening of bacterial candidate probiotics for marine fish larviculture. To reduce the number of candidate probiotics to be tested in vivo, various in vitro experiments need to be conducted, each screening for a particular mode of action – antagonism towards pathogen through production of antimicrobial compounds, growth and attachment to fish intestinal mucus, and the production of other beneficial compounds such as vitamins, fatty-acids and digestive enzymes. A total of 108 bacteria species were isolated from the digestive tract of the adult common clownfish, Amphiprion percula to screen for potential probiotics to be used in clownfish larval rearing. The antagonistic compounds assay identified twelve isolates which showed antagonism towards two or more aquatic pathogens. This was followed by an in vitro test that involved growing the organisms in fish intestinal mucus and modeling their growth parameters. A ranking index (RI) was developed using the lag period (λ) and doubling time (td) of the organism, where (1over λ x td) x 100. Five candidate probionts (AP1-AP5) with varied growth parameters were used for further in vitro experiments. The attachment to mucus assay introduced a novel tool for quantifying competition for attachment sites between candidate probionts and pathogens on mucus. Candidate probiont Pseudoalteromonas AP5 reduced the attachment ability of Vibrio alginolyticus when added before the pathogen and partially out-competed the pathogen for attachment sites when added second. In vitro screening for the production of beneficial compounds tested the candidate probiotics’ ability to produce digestive enzymes - trypsin, lipase and alkaline phosphatase as well as carotenoids and vitamin C. Candidate probiont Pseudoalteromonas AP5 produced high levels of the enzymes (98.2, 34.1 and 91.3 mU product liberated.ml⁻¹, respectively) and contained carotenoids while Kocuria AP4 contained carotenoids but produced low quantities of enzymes (7.8, 0 and 59 mU product liberated.ml⁻¹, respectively). None of the candidate probiotics produced vitamin C. To eliminate potential pathogenic or toxic candidate probionts, Artemia nauplii were exposed to each candidate probiont and the percentage Artemia mortality after 24-hours was determined. Candidate probiont AP2 caused high mortality of Artemia nauplii (98.4%) and was excluded from further studies. Identification of candidate probionts AP3-AP5 was performed using 16S-rDNA molecular techniques and the bacteria were assigned the names Bacillus AP3, Kocuria AP4 and Pseudoalteromonas AP5, respectively. Two methods of larval probiont delivery were tested – attachment to Artemia, and in-water delivery. Attachment to Artemia was high for both Kocuria AP4 and Pseudoalteromonas AP5 (7.2 x10³ and 2.7x10⁴ bacteria.nauplius⁻¹, respectively) while the in-water viability experiment showed that Kocuria AP4 comprised 23.9% of the total culturable water microflora after 24 hours while Pseudoalteromonas AP5 contributed 100%. To validate the findings from the in vitro experiments, in vivo trials using clownfish larvae were performed. Of the four candidate probiotics tested, only Kocuria AP4 showed potential to increase larval survival. In vitro tests produced a better understanding of the possible mode of action and strategies of competition between bacteria, however, the number of criteria in which a candidate probiont is successful in vitro may not be the best predictor for its effectiveness in vivo. Commercial studies that reduce between-treatment variation are required to test predictions about the most suitable probiont or combinations thereof.
- Full Text:
- Date Issued: 2005