The biology and movement patterns of non-native common carp, cyprinus carpio (l) in Groenvlei, South Africa
- Authors: Mukhari, Dinah Lorraine
- Date: 2022-04-06
- Subjects: Carp South Africa Goukamma Nature Reserve , Introduced fishes South Africa Goukamma Nature Reserve , Carp Behavior South Africa Goukamma Nature Reserve , Carp South Africa Goukamma Nature Reserve Growth , Carp Habitat South Africa Goukamma Nature Reserve , Carp South Africa Goukamma Nature Reserve Reproduction , Habitat conservation South Africa Goukamma Nature Reserve , Aquatic resources conservation South Africa Goukamma Nature Reserve
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/291233 , vital:56834
- Description: The common carp, Cyprinus carpio is a highly invasive fish species, first introduced into South Africa in the late nineteen century, and now widely spread throughout the country. In 1991 carp were illegally introduced to Groenvlei, within the Goukamma Nature Reserve in the Western Cape Province. Decreases in water quality and declines in biota have been attributed to the now large numbers of carp. Management measures have commenced to reduce the carp population, however these are not underpinned by science as little is known about the biology and movement patterns of resident carp. The age, growth and maturity of carp within the lake was determined using oxytetracycline hydrochloride marked asteriscus otoliths and macroscopic gonad development staging methods. The results showed that carp in Groenvlei had similar growth characteristics to the invasive populations in North America and Australia; fast growth during the first three to five years and reproductive maturity attained between the ages of two to three years, and are long lived (maximum age of 20 years old). Their growth however differed from the only other study on a South African population. Six acoustically tagged carp were manually tracked in order to report on their movement patterns and habitat use. Carp moved much greater distances in February compared to October and November, and occupied different areas of the lake. In November they were found to aggregate in backwaters which corresponds with their breeding activities. Literature on global carp control shows that whilst eradication of this fish can be achieved in small isolated waters using icthyocides and water drawdowns, in conservation priority areas such as Groenvlei where this is not possible, mechanical removal using multiple gears targeting vulnerable life stages can most efficient at controlling carp. This study identified where and when these methods could be focused to optimise control efforts. , Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries Science, 2022
- Full Text:
- Authors: Mukhari, Dinah Lorraine
- Date: 2022-04-06
- Subjects: Carp South Africa Goukamma Nature Reserve , Introduced fishes South Africa Goukamma Nature Reserve , Carp Behavior South Africa Goukamma Nature Reserve , Carp South Africa Goukamma Nature Reserve Growth , Carp Habitat South Africa Goukamma Nature Reserve , Carp South Africa Goukamma Nature Reserve Reproduction , Habitat conservation South Africa Goukamma Nature Reserve , Aquatic resources conservation South Africa Goukamma Nature Reserve
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/291233 , vital:56834
- Description: The common carp, Cyprinus carpio is a highly invasive fish species, first introduced into South Africa in the late nineteen century, and now widely spread throughout the country. In 1991 carp were illegally introduced to Groenvlei, within the Goukamma Nature Reserve in the Western Cape Province. Decreases in water quality and declines in biota have been attributed to the now large numbers of carp. Management measures have commenced to reduce the carp population, however these are not underpinned by science as little is known about the biology and movement patterns of resident carp. The age, growth and maturity of carp within the lake was determined using oxytetracycline hydrochloride marked asteriscus otoliths and macroscopic gonad development staging methods. The results showed that carp in Groenvlei had similar growth characteristics to the invasive populations in North America and Australia; fast growth during the first three to five years and reproductive maturity attained between the ages of two to three years, and are long lived (maximum age of 20 years old). Their growth however differed from the only other study on a South African population. Six acoustically tagged carp were manually tracked in order to report on their movement patterns and habitat use. Carp moved much greater distances in February compared to October and November, and occupied different areas of the lake. In November they were found to aggregate in backwaters which corresponds with their breeding activities. Literature on global carp control shows that whilst eradication of this fish can be achieved in small isolated waters using icthyocides and water drawdowns, in conservation priority areas such as Groenvlei where this is not possible, mechanical removal using multiple gears targeting vulnerable life stages can most efficient at controlling carp. This study identified where and when these methods could be focused to optimise control efforts. , Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries Science, 2022
- Full Text:
The diversity and dry season habitat associations of fish communities in the Kabompo River Basin, Upper Zambezi, Zambia
- Authors: Rennie, Craig Lawrence
- Date: 2022-04-06
- Subjects: Biodiversity Zambia Kabompo District , Ecology Zambia Kabompo District , Fish communities Zambia Kabompo District , Fishes Ecology Zambia Kabompo District , Freshwater habitats Zambia Kabompo District , Fishes Effect of human beings on Zambia Kabompo District , Fishes Climatic factors Zambia Kabompo District , Mesohabitat
- Language: English
- Type: Master's thesis , text
- Identifier: http://hdl.handle.net/10962/232261 , vital:49976
- Description: The Zambezian headwaters contain diverse fish communities which support thriving fisheries. This region and its fishes are under pressure from multiple anthropogenic threats, including overexploitation and large-scale developments with potential knock-on effects for the riparian communities. Previous studies have focused on known fisheries areas and the mainstem Zambezi River, neglecting large tributaries such as the Kabompo River. Consequently, little literature is available on the diversity and ecology of the fishes that inhabit these large tributaries, hindering the effective management and protection of biodiversity. This study aimed to fill the current knowledge gaps in the diversity and habitat associations of fish communities in the Upper Zambezi, using the Kabompo River as a case study. The first objective was to provide an updated checklist of the fishes of the Kabompo River basin using a compilation of historical data and field surveys. This study detailed the occurrence and distribution of 83 fish species within the Kabompo River basin. All these species have been recorded in the Upper Zambezi, with some of their ranges extending into the Middle (29 species) and Lower Zambezi (23 species) while others have more restricted distributions. The most diverse families were the Cyprinidae (26 species) and the Cichlidae (15 species). A number of potential undescribed species, whose taxonomic distinctiveness need further investigation were also collected. Taxonomic conflicts are also highlighted for some of the taxa that were previously considered to have broad geographic ranges or disjunct distributions. Consistent with findings from other studies within the region, the current taxonomy underestimates the diversity of fishes in the Kabompo River and Upper Zambezi. The second objective was to assess the habitat use of small-bodied fish communities during the low-flow period in 2019. Reconnaissance trips identified dominant mesohabitats along the middle Kabompo River around Jivundu. A total of 139 mesohabitats were sampled across the five dominant mesohabitats identified; Phragmites mauritianus, wood, rock, Vallisneria aethiopica and bare substrate. Catch per unit effort, species richness, Shannon diversity and Pielou’s evenness differed significantly between these mesohabitats. Twenty-six species showed significant associations (p < 0.05) with a specific mesohabitat type or environmental variable (current velocity or depth). Eight species were associated with the woody habitat, with three of these, E. radiatus, E. unitaeniatus, and P. ngamensis being almost exclusively associated with this habitat. Enteromius kerstenii, E. lineomaculatus and S. depressirostris were almost exclusively associated with P. mauritianus and represent potential indicator species for this habitat. A number of species were also with both P. mauritianus and woody habitats. Nine species showed statistically significant associations with the rocky mesohabitat, with Amphilius uranoscopus and Petrocephalus longicapitis, being almost exclusive to rocky sections of the river. Therefore, species such as A. uranoscopus are potential indicators for monitoring the integrity of rocky habitats under threat from sedimentation. The strong associations indicate that this comprehensive baseline may be valuable indicators/ proxies for identifying anthropogenic induced change in the Kabompo basin. This would provide a basis to determine fish responses to regional environmental changes associated with human activities. , Thesis (MSc) -- Faculty of Science, Ichthyology & Fisheries Science, 2022
- Full Text:
- Authors: Rennie, Craig Lawrence
- Date: 2022-04-06
- Subjects: Biodiversity Zambia Kabompo District , Ecology Zambia Kabompo District , Fish communities Zambia Kabompo District , Fishes Ecology Zambia Kabompo District , Freshwater habitats Zambia Kabompo District , Fishes Effect of human beings on Zambia Kabompo District , Fishes Climatic factors Zambia Kabompo District , Mesohabitat
- Language: English
- Type: Master's thesis , text
- Identifier: http://hdl.handle.net/10962/232261 , vital:49976
- Description: The Zambezian headwaters contain diverse fish communities which support thriving fisheries. This region and its fishes are under pressure from multiple anthropogenic threats, including overexploitation and large-scale developments with potential knock-on effects for the riparian communities. Previous studies have focused on known fisheries areas and the mainstem Zambezi River, neglecting large tributaries such as the Kabompo River. Consequently, little literature is available on the diversity and ecology of the fishes that inhabit these large tributaries, hindering the effective management and protection of biodiversity. This study aimed to fill the current knowledge gaps in the diversity and habitat associations of fish communities in the Upper Zambezi, using the Kabompo River as a case study. The first objective was to provide an updated checklist of the fishes of the Kabompo River basin using a compilation of historical data and field surveys. This study detailed the occurrence and distribution of 83 fish species within the Kabompo River basin. All these species have been recorded in the Upper Zambezi, with some of their ranges extending into the Middle (29 species) and Lower Zambezi (23 species) while others have more restricted distributions. The most diverse families were the Cyprinidae (26 species) and the Cichlidae (15 species). A number of potential undescribed species, whose taxonomic distinctiveness need further investigation were also collected. Taxonomic conflicts are also highlighted for some of the taxa that were previously considered to have broad geographic ranges or disjunct distributions. Consistent with findings from other studies within the region, the current taxonomy underestimates the diversity of fishes in the Kabompo River and Upper Zambezi. The second objective was to assess the habitat use of small-bodied fish communities during the low-flow period in 2019. Reconnaissance trips identified dominant mesohabitats along the middle Kabompo River around Jivundu. A total of 139 mesohabitats were sampled across the five dominant mesohabitats identified; Phragmites mauritianus, wood, rock, Vallisneria aethiopica and bare substrate. Catch per unit effort, species richness, Shannon diversity and Pielou’s evenness differed significantly between these mesohabitats. Twenty-six species showed significant associations (p < 0.05) with a specific mesohabitat type or environmental variable (current velocity or depth). Eight species were associated with the woody habitat, with three of these, E. radiatus, E. unitaeniatus, and P. ngamensis being almost exclusively associated with this habitat. Enteromius kerstenii, E. lineomaculatus and S. depressirostris were almost exclusively associated with P. mauritianus and represent potential indicator species for this habitat. A number of species were also with both P. mauritianus and woody habitats. Nine species showed statistically significant associations with the rocky mesohabitat, with Amphilius uranoscopus and Petrocephalus longicapitis, being almost exclusive to rocky sections of the river. Therefore, species such as A. uranoscopus are potential indicators for monitoring the integrity of rocky habitats under threat from sedimentation. The strong associations indicate that this comprehensive baseline may be valuable indicators/ proxies for identifying anthropogenic induced change in the Kabompo basin. This would provide a basis to determine fish responses to regional environmental changes associated with human activities. , Thesis (MSc) -- Faculty of Science, Ichthyology & Fisheries Science, 2022
- Full Text:
The biology of Oreochromis mossambicus and vulnerability to the invasion of Oreochromis niloticus
- Authors: Mpanza, Nobuhle Phumzile
- Date: 2022-10-14
- Subjects: Ecomorphology , Mozambique tilapia , Nile tilapia , Introduced fishes , Predatory aquatic animals , Predation (Biology) , Otoliths , Von Bertalanffy function
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/362983 , vital:65380
- Description: Mozambique tilapia, Oreochromis mossambicus, a native southern African species now co-occurs with invasive Nile tilapia, Oreochromis niloticus throughout much of the distribution of the former. The spread of O. niloticus in South Africa has been attributed to escapees from aquaculture facilities, placing O. mossambicus at risk through competition for habitat and food resources, as well as through hybridisation. To better manage invasions, a comprehensive understanding of the biology, ecology and behaviour of both native and invasive species is required. The aim of this research was to comparatively assess the biology of O. mossambicus and O. niloticus, their food resource use characteristics and potential competitive interactions to infer impact risks associated with O. niloticus invasion dynamics. In addition to lack of sufficient autecological knowledge on O. niloticus in general, the challenge in the Eastern Cape is that relatively little regional knowledge is available on the biology and ecology of the native O. mossambicus. To address this, a total of 101 O. mossambicus individuals (32 - 297 mm LT) were sampled from the Sunday River catchment and their age and growth determined using sectioned sagittal otoliths. The largest female was 288.8 mm with a parameter estimate of LT (mm) = 272 (1-e-0.331(t=0.772)) and the largest male was 297 mm described as LT (mm) = 331.9 (1-e-0.167(t=1.192)). The growth parameter estimate age for combined sexes was best described as LT (mm) = 322.5 (1-e-0.201(t=1.027)). The growth rate was initially rapid for O. mossambicus and the asymptotic length reached after four years. The length-at-50% maturity was reached at 106.45 mm LT (R2 = 0.57) for the entire population. There was a significant difference (ᵡ2 = 8,047, df = 1, p-value = 0.0045) in the sex ratio between males and females which was skewed towards males 1:1.89 (F:M). Comparisons with O. niloticus were based on literature and these showed that O. niloticus had faster growth rates than O. mossambicus. These results serve as a baseline study in predicting the potential impacts of O. niloticus if it was to be introduced in the Eastern Cape region. Furthermore, although these two species are known to share habitat and food resources, feeding dynamics within the context of relative impact on prey resources, and competition potential between the species, are largely lacking. I used experimental functional response procedures to contrast the food consumption dynamics of each species and to assess for any multiple predator effects (MPEs) between these two closely related fishes. This was done by contrasting functional responses between individual species under single predator scenarios, predicted multiple predator functional response dynamics based on the individual species outputs, and actually observed functional responses under multiple predator conditions. Results showed that both Nile tilapia and Mozambique tilapia depicted a destabilizing Type II functional response. In both single and conspecific pairing Nile tilapia had significantly greater functional responses than Mozambique tilapia, hence greater overall predatory potential than its native congeneric Mozambique tilapia. Attack rates were also greater for Nile tilapia than Mozambique tilapia with both species showing similar handling times in single trials. However, no evidence for MPEs were detected, given lack of differences between predicted and observed functional responses under heterospecific conditions. These results suggest that Nile tilapia do not adjust their food intake in the presence of heterospecific competitors, but do consume more than Mozambique tilapia and are better at finding food when it is present at low densities. Feeding-related morphological characteristics may influence predatory performance of a species and can further provide information on the species’ capacity to locate, attack and consume different prey items. The feeding capacities between O. mossambicus and O. niloticus were compared based on morphological traits in order to determine whether differences existed, and if these differences place the invasive O. niloticus at an advantageous position in terms of resource acquisition and consumption over its native congener. Principal component analysis for functional morphology traits showed overlap between O. niloticus and O. mossambicus. Oreochromis niloticus had distinctively larger lower jaw closing force, gill resistance and gill raker length which facilitated greater feeding capacities for the invasive species over the native O. mossambicus. Trophic profiles depicted high dietary overlap between the two species. Although O. niloticus had a greater feeding capacity towards phytoplankton, plants, fish (ambush), fish (pursuit) and larvae, while O. mossambicus only showed greater feeding capacity towards zooplankton. While dietary overlap and similarities in morphological traits between native and invasive species may result in exploitative competition between the species, O. niloticus seems to be more versatile in its feeding and capable of consuming food web components that O. mossambicus may not be able to handle. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2022
- Full Text:
- Authors: Mpanza, Nobuhle Phumzile
- Date: 2022-10-14
- Subjects: Ecomorphology , Mozambique tilapia , Nile tilapia , Introduced fishes , Predatory aquatic animals , Predation (Biology) , Otoliths , Von Bertalanffy function
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/362983 , vital:65380
- Description: Mozambique tilapia, Oreochromis mossambicus, a native southern African species now co-occurs with invasive Nile tilapia, Oreochromis niloticus throughout much of the distribution of the former. The spread of O. niloticus in South Africa has been attributed to escapees from aquaculture facilities, placing O. mossambicus at risk through competition for habitat and food resources, as well as through hybridisation. To better manage invasions, a comprehensive understanding of the biology, ecology and behaviour of both native and invasive species is required. The aim of this research was to comparatively assess the biology of O. mossambicus and O. niloticus, their food resource use characteristics and potential competitive interactions to infer impact risks associated with O. niloticus invasion dynamics. In addition to lack of sufficient autecological knowledge on O. niloticus in general, the challenge in the Eastern Cape is that relatively little regional knowledge is available on the biology and ecology of the native O. mossambicus. To address this, a total of 101 O. mossambicus individuals (32 - 297 mm LT) were sampled from the Sunday River catchment and their age and growth determined using sectioned sagittal otoliths. The largest female was 288.8 mm with a parameter estimate of LT (mm) = 272 (1-e-0.331(t=0.772)) and the largest male was 297 mm described as LT (mm) = 331.9 (1-e-0.167(t=1.192)). The growth parameter estimate age for combined sexes was best described as LT (mm) = 322.5 (1-e-0.201(t=1.027)). The growth rate was initially rapid for O. mossambicus and the asymptotic length reached after four years. The length-at-50% maturity was reached at 106.45 mm LT (R2 = 0.57) for the entire population. There was a significant difference (ᵡ2 = 8,047, df = 1, p-value = 0.0045) in the sex ratio between males and females which was skewed towards males 1:1.89 (F:M). Comparisons with O. niloticus were based on literature and these showed that O. niloticus had faster growth rates than O. mossambicus. These results serve as a baseline study in predicting the potential impacts of O. niloticus if it was to be introduced in the Eastern Cape region. Furthermore, although these two species are known to share habitat and food resources, feeding dynamics within the context of relative impact on prey resources, and competition potential between the species, are largely lacking. I used experimental functional response procedures to contrast the food consumption dynamics of each species and to assess for any multiple predator effects (MPEs) between these two closely related fishes. This was done by contrasting functional responses between individual species under single predator scenarios, predicted multiple predator functional response dynamics based on the individual species outputs, and actually observed functional responses under multiple predator conditions. Results showed that both Nile tilapia and Mozambique tilapia depicted a destabilizing Type II functional response. In both single and conspecific pairing Nile tilapia had significantly greater functional responses than Mozambique tilapia, hence greater overall predatory potential than its native congeneric Mozambique tilapia. Attack rates were also greater for Nile tilapia than Mozambique tilapia with both species showing similar handling times in single trials. However, no evidence for MPEs were detected, given lack of differences between predicted and observed functional responses under heterospecific conditions. These results suggest that Nile tilapia do not adjust their food intake in the presence of heterospecific competitors, but do consume more than Mozambique tilapia and are better at finding food when it is present at low densities. Feeding-related morphological characteristics may influence predatory performance of a species and can further provide information on the species’ capacity to locate, attack and consume different prey items. The feeding capacities between O. mossambicus and O. niloticus were compared based on morphological traits in order to determine whether differences existed, and if these differences place the invasive O. niloticus at an advantageous position in terms of resource acquisition and consumption over its native congener. Principal component analysis for functional morphology traits showed overlap between O. niloticus and O. mossambicus. Oreochromis niloticus had distinctively larger lower jaw closing force, gill resistance and gill raker length which facilitated greater feeding capacities for the invasive species over the native O. mossambicus. Trophic profiles depicted high dietary overlap between the two species. Although O. niloticus had a greater feeding capacity towards phytoplankton, plants, fish (ambush), fish (pursuit) and larvae, while O. mossambicus only showed greater feeding capacity towards zooplankton. While dietary overlap and similarities in morphological traits between native and invasive species may result in exploitative competition between the species, O. niloticus seems to be more versatile in its feeding and capable of consuming food web components that O. mossambicus may not be able to handle. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2022
- Full Text:
- «
- ‹
- 1
- ›
- »