The feeding biology and potential impact of introduced giraffe (Giraffa camelopardalis) in the Eastern Cape Province, South Africa
- Authors: Parker, Daniel Matthew
- Date: 2004
- Subjects: Giraffe -- South Africa -- Eastern Cape , Animal-plant relationships -- South Africa -- Eastern Cape , Giraffe -- Food -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5694 , http://hdl.handle.net/10962/d1005380
- Description: Giraffe (Giraffa camelopardalis) are extralimital (non-native) to the Eastern Cape Province, South Africa yet they have and continue to be introduced to the region. Financial gain has arguably been the driving force behind these introductions as foreign tourists associate giraffe with Africa and the African wildlife experience. This raises a number of ethical, ecological and philosophical questions especially when it is considered that the impact of these browsers on the indigenous vegetation has remained largely unquantified. In this study I assessed the diet and potential impact of three populations of giraffe in the Eastern Cape Province between January 2002 and October 2003. The diet was assessed by both direct observations and faecal analysis. There was no significant difference (P > 0.05) between the results of the two methods of analysis, although direct observations appeared to be a superior method for assessing the diet of giraffe. The diet of giraffe in the Eastern Cape Province was similar to that within their native range with a deciduous species from the genus Acacia (Acacia karroo) being the most important component of the diet. However, giraffe in the Eastern Cape Province consumed more evergreen plant species than those within their native range. The relative lack of deciduous species in the Eastern Cape Province provides a likely explanation for such a result. Seasonal variation in the consumption of the most important species in the diet was evident and this was attributed to the deciduous nature of A. karroo and the seasonal growth of new shoots which were more palatable. The vegetation of the areas most commonly utilised by giraffe at each site was sampled using the point-centred-quarter method and the results related to the frequency of each species in the diet to calculate preference indices. Giraffe preference was strongest for A. karroo and this was attributed to the highly favourable chemical composition of the species. The browse utilisation of giraffe at each site was determined using the twig-length method and intake rates for the three most important species in the diet calculated using a pre-existing regression equation. Male giraffe fed at a higher rate than females. This was probably due to males adopting a “time-minimising” strategy to their feeding in order to allow more time for reproductive pursuits. Giraffe browse utilisation was highest where giraffe density was highest. However, several species were more heavily browsed than others even when giraffe density was low, suggesting that giraffe are capable of negatively affecting the indigenous flora of the province. I conclude that giraffe numbers should be reduced relative to property size in the Eastern Cape Province and that research into the impact of not only giraffe but the combined effects of giraffe and other extralimital herbivores on the indigenous flora and fauna be continued.
- Full Text:
- Date Issued: 2004
- Authors: Parker, Daniel Matthew
- Date: 2004
- Subjects: Giraffe -- South Africa -- Eastern Cape , Animal-plant relationships -- South Africa -- Eastern Cape , Giraffe -- Food -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5694 , http://hdl.handle.net/10962/d1005380
- Description: Giraffe (Giraffa camelopardalis) are extralimital (non-native) to the Eastern Cape Province, South Africa yet they have and continue to be introduced to the region. Financial gain has arguably been the driving force behind these introductions as foreign tourists associate giraffe with Africa and the African wildlife experience. This raises a number of ethical, ecological and philosophical questions especially when it is considered that the impact of these browsers on the indigenous vegetation has remained largely unquantified. In this study I assessed the diet and potential impact of three populations of giraffe in the Eastern Cape Province between January 2002 and October 2003. The diet was assessed by both direct observations and faecal analysis. There was no significant difference (P > 0.05) between the results of the two methods of analysis, although direct observations appeared to be a superior method for assessing the diet of giraffe. The diet of giraffe in the Eastern Cape Province was similar to that within their native range with a deciduous species from the genus Acacia (Acacia karroo) being the most important component of the diet. However, giraffe in the Eastern Cape Province consumed more evergreen plant species than those within their native range. The relative lack of deciduous species in the Eastern Cape Province provides a likely explanation for such a result. Seasonal variation in the consumption of the most important species in the diet was evident and this was attributed to the deciduous nature of A. karroo and the seasonal growth of new shoots which were more palatable. The vegetation of the areas most commonly utilised by giraffe at each site was sampled using the point-centred-quarter method and the results related to the frequency of each species in the diet to calculate preference indices. Giraffe preference was strongest for A. karroo and this was attributed to the highly favourable chemical composition of the species. The browse utilisation of giraffe at each site was determined using the twig-length method and intake rates for the three most important species in the diet calculated using a pre-existing regression equation. Male giraffe fed at a higher rate than females. This was probably due to males adopting a “time-minimising” strategy to their feeding in order to allow more time for reproductive pursuits. Giraffe browse utilisation was highest where giraffe density was highest. However, several species were more heavily browsed than others even when giraffe density was low, suggesting that giraffe are capable of negatively affecting the indigenous flora of the province. I conclude that giraffe numbers should be reduced relative to property size in the Eastern Cape Province and that research into the impact of not only giraffe but the combined effects of giraffe and other extralimital herbivores on the indigenous flora and fauna be continued.
- Full Text:
- Date Issued: 2004
The occurrence of Nosema apis (Zander), Acarapis woodi (Rennie), and the Cape problem bee in the summer rainfall region of South Africa
- Authors: Swart, Dawid Johannes
- Date: 2004
- Subjects: Nosema apis , Bee culture , Honeybee -- South Africa , Honeybee -- Diseases , Honeybee -- Parasites , Mites
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5914 , http://hdl.handle.net/10962/d1015980
- Description: The occurrence of Nosema disease, tracheal mites and the “pseudo-parasitic” behaviour of Cape honeybee workers when placed amongst African honeybees – known as the Cape Bee Problem – were studied over a 18 month period. Three surveys, approximately 6 months apart were done. The aims of this study were to establish the distribution and severity of the diseases and compare the disease with the presence of the Cape Bee Problem. Before this survey commenced European Foul Brood disease, Sacbrood (virus), Nosema, Brood nosema, and Tracheal mite have sporadically been reported in the summer rainfall region of South Africa. In the first survey 1005 colonies in 61 apiaries were surveyed, 803 colonies in 57 apiaries in the second, and 458 colonies in 41 apiaries in the third. Samples for disease and parasite analysis were taken at 4 colonies per apiary. Ten colonies per apiary were inspected for Cape Problem Bees, and samples of workers were collected and dissected at each of these colonies. Even with the addition of apiaries to 'fill-up' lost colonies during the second survey, 63% of all colonies were lost by the third survey. There was only a small difference in colony loss between sedentary and migratory beekeepers of 22% compared to 27%. Nosema was more prevalent amongst commercial beekeepers and increased in migratory operations during the survey period. The percentage of colonies infected increased during the survey period from 23% to 32% to 34%. The placement of colonies in Eucalyptus plantations may boost infection. Trachea mites seem to have spread quite rapidly in South Africa since its discovery. This parasitic mite was present in all regions, although in low numbers in three most northern regions. Sedentary colonies had higher levels of infestation than migratory colonies. The number of colonies infested diminished over the survey period, which may be a result of general colony loss. The Cape Problem Bee was less of a problem than anticipated. Colonies succumbed to Cape Problem Bees in all regions. When beekeepers reported high levels of infestation in their bee stocks the colonies would be dead within six months. In apiaries with low infestation the die-out was slower.
- Full Text:
- Date Issued: 2004
- Authors: Swart, Dawid Johannes
- Date: 2004
- Subjects: Nosema apis , Bee culture , Honeybee -- South Africa , Honeybee -- Diseases , Honeybee -- Parasites , Mites
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5914 , http://hdl.handle.net/10962/d1015980
- Description: The occurrence of Nosema disease, tracheal mites and the “pseudo-parasitic” behaviour of Cape honeybee workers when placed amongst African honeybees – known as the Cape Bee Problem – were studied over a 18 month period. Three surveys, approximately 6 months apart were done. The aims of this study were to establish the distribution and severity of the diseases and compare the disease with the presence of the Cape Bee Problem. Before this survey commenced European Foul Brood disease, Sacbrood (virus), Nosema, Brood nosema, and Tracheal mite have sporadically been reported in the summer rainfall region of South Africa. In the first survey 1005 colonies in 61 apiaries were surveyed, 803 colonies in 57 apiaries in the second, and 458 colonies in 41 apiaries in the third. Samples for disease and parasite analysis were taken at 4 colonies per apiary. Ten colonies per apiary were inspected for Cape Problem Bees, and samples of workers were collected and dissected at each of these colonies. Even with the addition of apiaries to 'fill-up' lost colonies during the second survey, 63% of all colonies were lost by the third survey. There was only a small difference in colony loss between sedentary and migratory beekeepers of 22% compared to 27%. Nosema was more prevalent amongst commercial beekeepers and increased in migratory operations during the survey period. The percentage of colonies infected increased during the survey period from 23% to 32% to 34%. The placement of colonies in Eucalyptus plantations may boost infection. Trachea mites seem to have spread quite rapidly in South Africa since its discovery. This parasitic mite was present in all regions, although in low numbers in three most northern regions. Sedentary colonies had higher levels of infestation than migratory colonies. The number of colonies infested diminished over the survey period, which may be a result of general colony loss. The Cape Problem Bee was less of a problem than anticipated. Colonies succumbed to Cape Problem Bees in all regions. When beekeepers reported high levels of infestation in their bee stocks the colonies would be dead within six months. In apiaries with low infestation the die-out was slower.
- Full Text:
- Date Issued: 2004
The toxic effect of heavy metals on algal biomass (Spirulina sp.) and carbonic anhydrase activity, an enzyme which is central to algal application in metal precipitation
- Authors: Nightingale, Leigh
- Date: 2004
- Subjects: Heavy metals -- Toxicology , Spirulina , Carbonic anhydrase , Algae -- Metabolism , Photosynthesis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4093 , http://hdl.handle.net/10962/d1007858 , Heavy metals -- Toxicology , Spirulina , Carbonic anhydrase , Algae -- Metabolism , Photosynthesis
- Description: Acid rmne drainage (AMD) is a major pollution problem througbout the world, adversely affecting both surface and groundwaters. AMD is principally associated with the mining of sulphide ores. The most commonly associated minerals being sulphur, copper, zinc, silver, gold, lead and uranium. As conventional methods for removing heavy metals from wastewater are often prohibitively expensive, the implementation of biological processes for the removal of heavy metals has become a realistic practice. The objectives of this project was firstly to establish the effect of copper, lead and nickel, heavy metals commonly found in AMD waters, on the enzyme carbonic anhydrase, which is an integral part of the carbon concentrating mechanism (CCM) and secondly, to determine the feasibility of using the alkalinity generated by Spindina for the precipitation of heavy metals from solution. Initially, batch flask experiments were performed and it was found that the algae were able to utilise the bicarbonate supplied in the medium, under CO, limiting conditions, through the induction of their CCM, resulting in the generation of carbonate. The effect of the inhibitors, acetazolamide (AZ) and ethoxyzolamide (EZ), were also investigated in order to determine the importance of carbonic anhydrase (CA) in inorganic carbon accumulation and photosynthesis. Results obtained were consistent with those observed in literature and it was found that at IOOf.LM AZ and EZ, complete inhibition of photosynthesis and carbonic anhydrase occurred, with no oxygen being evolved. The results obtained from the inhibitor experiments substantiate the findings that carbonic anhydrase is an important part of the CCM, and that the dehydration of bicarbonate to carbon dioxide and hydroxide ions, is in fact an enzymatic process regulated by the enzyme carbonic anhydrase and is essential for efficient photosynthesis. The effect of heavy metals on Spirulina was also investigated. Lead, copper and nickel were all found to cause a reduction in the synthesis of chlorophyll a, which resulted in a decrease in photosynthetic efficiency and eventually death of the culture. The morphology of the algae was also severely affected by heavy metals, with degradation and aJmost complete disintegration of the algal filaments occurring. Using the Wilbur-Anderson assay method, carbonic anhydrase activity was found to be lower in the experimental flasks containing heavy metals, than the control flasks, reducing the algae's ability to utilise the bicarbonate in solution for effective photosynthesis. The Wilbur-Anderson assay method did not prove to be a reliable method for measuring changes in enzyme activity as results were found to be erratic. Therefore attempts were made to use an oxygen electrode as an alternative method for determining the effects of various parameters on enzyme activity and photosynthesis, this proved to be more successful. Because of the toxic effects of heavy metals on Spirulina it was decided that the use of the biogenic alkalinity generated by the algae for the precipitation of heavy metals may be successfully employed as an alternative method for bioremediation and metal recovery. Carbonate reacts readily with metals, therefore the carbonate produced by this algal system was used for the precipitation of metals. It was possible to categorise the precipitation reactions observed into three groups, namely those metals which, a) precipitate as hydroxides, b) precipitate as carbonates generated from the dissociation of bicarbonate and c) metals which can only precipitate if there is free carbonate present in solution.
- Full Text:
- Date Issued: 2004
- Authors: Nightingale, Leigh
- Date: 2004
- Subjects: Heavy metals -- Toxicology , Spirulina , Carbonic anhydrase , Algae -- Metabolism , Photosynthesis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4093 , http://hdl.handle.net/10962/d1007858 , Heavy metals -- Toxicology , Spirulina , Carbonic anhydrase , Algae -- Metabolism , Photosynthesis
- Description: Acid rmne drainage (AMD) is a major pollution problem througbout the world, adversely affecting both surface and groundwaters. AMD is principally associated with the mining of sulphide ores. The most commonly associated minerals being sulphur, copper, zinc, silver, gold, lead and uranium. As conventional methods for removing heavy metals from wastewater are often prohibitively expensive, the implementation of biological processes for the removal of heavy metals has become a realistic practice. The objectives of this project was firstly to establish the effect of copper, lead and nickel, heavy metals commonly found in AMD waters, on the enzyme carbonic anhydrase, which is an integral part of the carbon concentrating mechanism (CCM) and secondly, to determine the feasibility of using the alkalinity generated by Spindina for the precipitation of heavy metals from solution. Initially, batch flask experiments were performed and it was found that the algae were able to utilise the bicarbonate supplied in the medium, under CO, limiting conditions, through the induction of their CCM, resulting in the generation of carbonate. The effect of the inhibitors, acetazolamide (AZ) and ethoxyzolamide (EZ), were also investigated in order to determine the importance of carbonic anhydrase (CA) in inorganic carbon accumulation and photosynthesis. Results obtained were consistent with those observed in literature and it was found that at IOOf.LM AZ and EZ, complete inhibition of photosynthesis and carbonic anhydrase occurred, with no oxygen being evolved. The results obtained from the inhibitor experiments substantiate the findings that carbonic anhydrase is an important part of the CCM, and that the dehydration of bicarbonate to carbon dioxide and hydroxide ions, is in fact an enzymatic process regulated by the enzyme carbonic anhydrase and is essential for efficient photosynthesis. The effect of heavy metals on Spirulina was also investigated. Lead, copper and nickel were all found to cause a reduction in the synthesis of chlorophyll a, which resulted in a decrease in photosynthetic efficiency and eventually death of the culture. The morphology of the algae was also severely affected by heavy metals, with degradation and aJmost complete disintegration of the algal filaments occurring. Using the Wilbur-Anderson assay method, carbonic anhydrase activity was found to be lower in the experimental flasks containing heavy metals, than the control flasks, reducing the algae's ability to utilise the bicarbonate in solution for effective photosynthesis. The Wilbur-Anderson assay method did not prove to be a reliable method for measuring changes in enzyme activity as results were found to be erratic. Therefore attempts were made to use an oxygen electrode as an alternative method for determining the effects of various parameters on enzyme activity and photosynthesis, this proved to be more successful. Because of the toxic effects of heavy metals on Spirulina it was decided that the use of the biogenic alkalinity generated by the algae for the precipitation of heavy metals may be successfully employed as an alternative method for bioremediation and metal recovery. Carbonate reacts readily with metals, therefore the carbonate produced by this algal system was used for the precipitation of metals. It was possible to categorise the precipitation reactions observed into three groups, namely those metals which, a) precipitate as hydroxides, b) precipitate as carbonates generated from the dissociation of bicarbonate and c) metals which can only precipitate if there is free carbonate present in solution.
- Full Text:
- Date Issued: 2004
Thermal and photostability studies of triprolidine hydrochloride and its mixtures with cyclodextrin and glucose
- Authors: Ndlebe, Vuyelwa Jacqueline
- Date: 2004
- Subjects: Antihistamines , Glucose , Cyclodextrins
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4387 , http://hdl.handle.net/10962/d1005052 , Antihistamines , Glucose , Cyclodextrins
- Description: Triprolidine hydrochloride (C₁₉H₂₂N₂.HCl.H₂O) (TPH) is a well-known antihistamine drug. It melts between 118°C and 122°C and the amount of water present is 4.5 mass percent. TPH is reported as being photosensitive and must be stored in sealed, light-tight containers. The thermal stabilities of TPH and of 1:1 molar and 1:1 mass ratio physical mixtures of TPH with beta-cyclodextrin (BCD) and with glucose have been examined using DSC, TG and TG-FTIR, complemented by X-ray powder diffraction (XRD) and infrared spectroscopic (IR) studies. Thermal studies of the solid TPH/BCD mixtures indicated that interaction between the components occurs and it is possible that the TPH molecule may be least partially accommodated in the cavity of the BCD host molecule. XRD results support this indication of inclusion. The results for mixtures of TPH/glucose also suggest that there is interaction between the two components. The results of molecular modelling suggest that TPH is most likely to be accommodated in the BCD cavity as a neutral triprolidine molecule with the toluene portion of the molecule entering first. There is also an indication that the Z-isomer should be accommodated slightly more readily than the E-isomer. Photostability studies were done by irradiating thin layers of solid samples of TPH and its mixtures for various times at 40°C using an Atlas Sun test CPS lamp operating at 550 W h m⁻². An analytical method using HPLC was developed and validated to determine the amounts of any photodegradants. DSC, TG, FTIR, XRD and IR were also used examine the irradiated samples. XRD results showed that changes in the TPH crystal structure occurred during irradiation and that these changes increased with the time of irradiation. Irradiation for 20 hours with UV or exposure to sunlight showed the presence of degradants. The results obtained illustrate the general stability of TPH, especially in the solid state. Although the potential for isomerization to the pharmaceutically inactive Z-isomer exists, this transformation would require extreme light conditions. The study has also shown TPH to be compatible with both glucose and BCD, which are potential excipients both in solid and liquid dosage forms. The presents of these excipients in dosage forms will thus not adversely affect the stability and the therapeutic efficacy of TPH. . An analytical method using HPLC was developed and validated to determine the amounts of any photodegradants. DSC, TG, FTIR, XRD and IR were also used examine the irradiated samples. XRD results showed that changes in the TPH crystal structure occurred during irradiation and that these changes increased with the time of irradiation. Irradiation for 20 hours with UV or exposure to sunlight showed the presence of degradants.
- Full Text:
- Date Issued: 2004
- Authors: Ndlebe, Vuyelwa Jacqueline
- Date: 2004
- Subjects: Antihistamines , Glucose , Cyclodextrins
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4387 , http://hdl.handle.net/10962/d1005052 , Antihistamines , Glucose , Cyclodextrins
- Description: Triprolidine hydrochloride (C₁₉H₂₂N₂.HCl.H₂O) (TPH) is a well-known antihistamine drug. It melts between 118°C and 122°C and the amount of water present is 4.5 mass percent. TPH is reported as being photosensitive and must be stored in sealed, light-tight containers. The thermal stabilities of TPH and of 1:1 molar and 1:1 mass ratio physical mixtures of TPH with beta-cyclodextrin (BCD) and with glucose have been examined using DSC, TG and TG-FTIR, complemented by X-ray powder diffraction (XRD) and infrared spectroscopic (IR) studies. Thermal studies of the solid TPH/BCD mixtures indicated that interaction between the components occurs and it is possible that the TPH molecule may be least partially accommodated in the cavity of the BCD host molecule. XRD results support this indication of inclusion. The results for mixtures of TPH/glucose also suggest that there is interaction between the two components. The results of molecular modelling suggest that TPH is most likely to be accommodated in the BCD cavity as a neutral triprolidine molecule with the toluene portion of the molecule entering first. There is also an indication that the Z-isomer should be accommodated slightly more readily than the E-isomer. Photostability studies were done by irradiating thin layers of solid samples of TPH and its mixtures for various times at 40°C using an Atlas Sun test CPS lamp operating at 550 W h m⁻². An analytical method using HPLC was developed and validated to determine the amounts of any photodegradants. DSC, TG, FTIR, XRD and IR were also used examine the irradiated samples. XRD results showed that changes in the TPH crystal structure occurred during irradiation and that these changes increased with the time of irradiation. Irradiation for 20 hours with UV or exposure to sunlight showed the presence of degradants. The results obtained illustrate the general stability of TPH, especially in the solid state. Although the potential for isomerization to the pharmaceutically inactive Z-isomer exists, this transformation would require extreme light conditions. The study has also shown TPH to be compatible with both glucose and BCD, which are potential excipients both in solid and liquid dosage forms. The presents of these excipients in dosage forms will thus not adversely affect the stability and the therapeutic efficacy of TPH. . An analytical method using HPLC was developed and validated to determine the amounts of any photodegradants. DSC, TG, FTIR, XRD and IR were also used examine the irradiated samples. XRD results showed that changes in the TPH crystal structure occurred during irradiation and that these changes increased with the time of irradiation. Irradiation for 20 hours with UV or exposure to sunlight showed the presence of degradants.
- Full Text:
- Date Issued: 2004
Towards sustainable utilisation of the fishery resources of the Kowie Estuary, South Africa
- Authors: Nsubuga, Yvonne Nakalo
- Date: 2004
- Subjects: Estuarine fisheries -- South Africa -- Eastern Cape -- Kowie Estuary , Estuarine ecology -- South Africa -- Eastern Cape -- Kowie Estuary
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4761 , http://hdl.handle.net/10962/d1007154 , Estuarine fisheries -- South Africa -- Eastern Cape -- Kowie Estuary , Estuarine ecology -- South Africa -- Eastern Cape -- Kowie Estuary
- Description: The annual biomass of fish caught from estuaries in South Africa is currently estimated at over 24,800 tons. These estuarine fishes are caught by over 73,000 fishers, most of them recreational. Annual income derived from South Africa’s total estuarine fishery was worth approximately R430,000,000 in 1997. There is increasing concern that unless our estuarine fisheries are effectively managed, we will not be able to sustain these benefits into the future. Two factors that contribute to inadequate management of the estuarine fisheries in South Africa are a lack of data on which to base management decisions, and the lack of indicators by which to assess trends towards sustainability. The main aims of this study were to provide a description of the Kowie estuary fishery, identify suitable indicators of sustainability for this fishery, and assess its sustainability. Boat-based and shore-based roving creel surveys were carried out on the Kowie estuary between July 2000 and June 2001; 1,091 interviews were conducted with linefishers, and 277 interviews with bait collectors. In the boat-based interviews, data were collected on fisher demographics, fishing site, fishing method, choice of bait, fishing duration and catch statistics. In the shore-based surveys, additional data were collected from shore-based linefishers and bait collectors on their perceptions, attitudes, and knowledge of fishery regulations. Total annual fishing effort on the Kowie estuary was estimated at 30,952 angler hours (SD=154); 84% of it recreational, and the rest subsistence. Most fishing occurred during December and January, and decreased during winter, especially June and July. The annual yield of fish from the estuary was estimated at 16,240 fish (SD=667) or 5.99 tons (SD=0.81). By number, recreational anglers caught 69% of the annual catch. Three species dominated the catch by number: Rhabdosargus holubi (62%), Pomadasys commersonnii (17%) and Argyrosomus japonicus (7%). By mass, the dominant species caught were Argyrosomus japonicus (60%) and Pomadasys commersonnii (19%). Overall catch rate on the estuary was 0.57 fish.ang.⁻¹h⁻¹ (SD=0.24), or 0.298 kg ang.⁻¹h⁻¹ (SD=0.31). Overall catch rate by number was highest in the subsistence sector at 1.13 fish.ang.⁻¹h⁻¹(SD=0.70), while the boat-based recreational sector recorded the highest overall catch rate by mass (0.427 kg.ang.⁻¹h⁻¹, SD=0.625). Argyrosomus japonicus had the highest overall catch rate by mass on the estuary (0.496 kg ang.⁻¹h⁻¹), and Rhabdosargus holubi the highest overall catch rate by number (1.233 fish.ang.⁻¹h⁻¹). Only 19% of the catch of R. holubi was above the minimum legal size, while the estimates for P. commersonnii and A. japonicus were 21% and 25%, respectively. The annual number of bait collecting outings on the estuary was estimated at 2,889, of which 75% were subsistence. The highest numbers of bait collecting outings were recorded in December and April. The Bay of Biscay was the most popular site for bait collecting. A total of five invertebrate species were collected from the estuary to be used as bait, of which the mud prawn Upogebia africana was the dominant species. Total annual number of mud prawns collected from the estuary was estimated at 260,648; of which 41% was collected by subsistence bait collectors. Thirteen indicators were selected to assess sustainability in three fishery sectors on the Kowie estuary: namely, the shore-based recreational linefishery, the subsistence linefishery and the subsistence bait fishery. Social sustainability was evaluated on the basis of the use fishery resources to fulfil Maslow's basic human needs of food and employment, safety and security, affiliation, self-esteem and selfactualisation. Indicators of ecosystem sustainability assessed the productivity, diversity, disturbance and degree of water quality in the estuary. Institutional sustainability was assessed on the basis that management systems in the fishery should be results-oriented, consent-based, truth-seeking and adaptable. Data on indicator performance was collected during the shore-based roving creel survey, and from published literature. Arbitrarily set reference points were used to assess indicator performance, which was graded on a scale from 1 (indicating minimum probability of sustainability) to 4 (indicating maximum probability of sustainability). Sustainability was illustrated with the aid of amoeba plots. Overall sustainability was low in all three fishery sectors investigated. Nine of the 13 indicators in the shore-based recreational fishery performed poorly, while 11 of 13 in the subsistence line fishery, and 10 of 13 in the subsistence bait fishery, performed poorly. In all three fishery sectors all four selected indicators of institutional sustainability performed poorly. The probability of social sustainability was higher in the shore-based recreational line fishery, where the performance of two of the five selected indicators was very good. The probability of ecological sustainability was lowest in the shore-based recreational linefishery, while in the subsistence linefishery only one selected indicator performed very well. Recommendations made towards assessing sustainability in small-scale estuarine fisheries include the formulation of national policy for assessing sustainability in fisheries, the involvement of fishers in the assessment process, use of fisher perceptions where data gaps exist, and the use of research results to guide future management decisions. Management changes recommended for the Kowie estuary fishery include the formulation of an effective and integrated management plan, identification of the key stakeholders in the fishery, inclusion of fishers in management, the protection of the estuary’s Zostera capensis beds, and the establishment of a programme to increase research and monitoring in the fishery.
- Full Text:
- Date Issued: 2004
- Authors: Nsubuga, Yvonne Nakalo
- Date: 2004
- Subjects: Estuarine fisheries -- South Africa -- Eastern Cape -- Kowie Estuary , Estuarine ecology -- South Africa -- Eastern Cape -- Kowie Estuary
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4761 , http://hdl.handle.net/10962/d1007154 , Estuarine fisheries -- South Africa -- Eastern Cape -- Kowie Estuary , Estuarine ecology -- South Africa -- Eastern Cape -- Kowie Estuary
- Description: The annual biomass of fish caught from estuaries in South Africa is currently estimated at over 24,800 tons. These estuarine fishes are caught by over 73,000 fishers, most of them recreational. Annual income derived from South Africa’s total estuarine fishery was worth approximately R430,000,000 in 1997. There is increasing concern that unless our estuarine fisheries are effectively managed, we will not be able to sustain these benefits into the future. Two factors that contribute to inadequate management of the estuarine fisheries in South Africa are a lack of data on which to base management decisions, and the lack of indicators by which to assess trends towards sustainability. The main aims of this study were to provide a description of the Kowie estuary fishery, identify suitable indicators of sustainability for this fishery, and assess its sustainability. Boat-based and shore-based roving creel surveys were carried out on the Kowie estuary between July 2000 and June 2001; 1,091 interviews were conducted with linefishers, and 277 interviews with bait collectors. In the boat-based interviews, data were collected on fisher demographics, fishing site, fishing method, choice of bait, fishing duration and catch statistics. In the shore-based surveys, additional data were collected from shore-based linefishers and bait collectors on their perceptions, attitudes, and knowledge of fishery regulations. Total annual fishing effort on the Kowie estuary was estimated at 30,952 angler hours (SD=154); 84% of it recreational, and the rest subsistence. Most fishing occurred during December and January, and decreased during winter, especially June and July. The annual yield of fish from the estuary was estimated at 16,240 fish (SD=667) or 5.99 tons (SD=0.81). By number, recreational anglers caught 69% of the annual catch. Three species dominated the catch by number: Rhabdosargus holubi (62%), Pomadasys commersonnii (17%) and Argyrosomus japonicus (7%). By mass, the dominant species caught were Argyrosomus japonicus (60%) and Pomadasys commersonnii (19%). Overall catch rate on the estuary was 0.57 fish.ang.⁻¹h⁻¹ (SD=0.24), or 0.298 kg ang.⁻¹h⁻¹ (SD=0.31). Overall catch rate by number was highest in the subsistence sector at 1.13 fish.ang.⁻¹h⁻¹(SD=0.70), while the boat-based recreational sector recorded the highest overall catch rate by mass (0.427 kg.ang.⁻¹h⁻¹, SD=0.625). Argyrosomus japonicus had the highest overall catch rate by mass on the estuary (0.496 kg ang.⁻¹h⁻¹), and Rhabdosargus holubi the highest overall catch rate by number (1.233 fish.ang.⁻¹h⁻¹). Only 19% of the catch of R. holubi was above the minimum legal size, while the estimates for P. commersonnii and A. japonicus were 21% and 25%, respectively. The annual number of bait collecting outings on the estuary was estimated at 2,889, of which 75% were subsistence. The highest numbers of bait collecting outings were recorded in December and April. The Bay of Biscay was the most popular site for bait collecting. A total of five invertebrate species were collected from the estuary to be used as bait, of which the mud prawn Upogebia africana was the dominant species. Total annual number of mud prawns collected from the estuary was estimated at 260,648; of which 41% was collected by subsistence bait collectors. Thirteen indicators were selected to assess sustainability in three fishery sectors on the Kowie estuary: namely, the shore-based recreational linefishery, the subsistence linefishery and the subsistence bait fishery. Social sustainability was evaluated on the basis of the use fishery resources to fulfil Maslow's basic human needs of food and employment, safety and security, affiliation, self-esteem and selfactualisation. Indicators of ecosystem sustainability assessed the productivity, diversity, disturbance and degree of water quality in the estuary. Institutional sustainability was assessed on the basis that management systems in the fishery should be results-oriented, consent-based, truth-seeking and adaptable. Data on indicator performance was collected during the shore-based roving creel survey, and from published literature. Arbitrarily set reference points were used to assess indicator performance, which was graded on a scale from 1 (indicating minimum probability of sustainability) to 4 (indicating maximum probability of sustainability). Sustainability was illustrated with the aid of amoeba plots. Overall sustainability was low in all three fishery sectors investigated. Nine of the 13 indicators in the shore-based recreational fishery performed poorly, while 11 of 13 in the subsistence line fishery, and 10 of 13 in the subsistence bait fishery, performed poorly. In all three fishery sectors all four selected indicators of institutional sustainability performed poorly. The probability of social sustainability was higher in the shore-based recreational line fishery, where the performance of two of the five selected indicators was very good. The probability of ecological sustainability was lowest in the shore-based recreational linefishery, while in the subsistence linefishery only one selected indicator performed very well. Recommendations made towards assessing sustainability in small-scale estuarine fisheries include the formulation of national policy for assessing sustainability in fisheries, the involvement of fishers in the assessment process, use of fisher perceptions where data gaps exist, and the use of research results to guide future management decisions. Management changes recommended for the Kowie estuary fishery include the formulation of an effective and integrated management plan, identification of the key stakeholders in the fishery, inclusion of fishers in management, the protection of the estuary’s Zostera capensis beds, and the establishment of a programme to increase research and monitoring in the fishery.
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- Date Issued: 2004