Assessing the effects of fish stock management on Cape gannet foraging behaviour in South Africa
- Strydom, Zanri, Grémillet, David, Pichegru, Lorien
- Authors: Strydom, Zanri , Grémillet, David , Pichegru, Lorien
- Date: 2023-12
- Subjects: Gannets -- South Africa , Birds of prey -- Behavior -- South Africa , Fish stock assessment
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/62622 , vital:72887
- Description: Seabirds are one of the most threatened groups of birds under both marine and terrestrial pressures. Among seabirds, the Cape gannet Morus capensis is a southern African endemic species facing several pressures of anthropogenic origin, including competition with industrial fisheries on small pelagic fish stocks. Cape gannets, being a long-lived species that is sensitive to environmental changes, are sentinels of change in oceanic environments granting it important to understand which factors influence their foraging behaviour and breeding outputs. For example, factors like age can result in a loss of physical capabilities which can lead to behavioral compensation and subsequent changes in chick provisioning rates and amounts. With the current fisheries management the fish stocks are continually decreasing, indicating the importance of an updated fine-scale assessment on the spatiotemporal overlap between foraging gannets and fisheries. The first objective of this thesis was to determine the influence of adult Cape gannets’ age and sex on their foraging characteristics and energy expenditure during foraging. I equipped chick-rearing Cape gannets of known age and sex with a 3D accelerometer and GPS device. Foraging effort (trip duration, foraging path and maximum distance to the nest) did not differ between sexes nor with age in Cape gannets. Both sexes rested less on the water with age. Aging females also spent more time in flight than males. The age- and sexual differences in energy expenditure prevalent in our study might reflect niche and/or risk partitioning strategies to ensure adequate provisioning to the chick. The second objective of this thesis was to determine the influence of fisheries catch rates, sardine and anchovy biomass, and adult foraging effort on chick growth rates in Cape gannets, using a long-term dataset collected between 2005 and 2020 on Malgas Island. I equipped chick-rearing adults with a GPS device and I weighed the chicks for between 3 to 6 increments to calculate the average daily mass increment. Of all the variables, foraging trip duration was the main determinant of daily growth rates, with chicks benefitting from parents’ shorter foraging trip durations. Chicks tended to grow slower when fisheries catch of sardine and anchovy were higher, possibly an effect of competition with fisheries. Chicks also grew faster when fish biomass was higher. This long-term monitoring demonstrated the possible effect of food competition between Cape gannets and fisheries, with negative impacts on gannet fitness as determined via chick growth rates. The third objective of this thesis was to determine the influence of both the biomass and fisheries catch rates of sardine and anchovy on Cape gannet foraging effort at a spatial and temporal scale. This was achieved by equipping a total of 668 chick-rearing Cape gannets with a GPS device. With an increase in fisheries catch there was an increase in the birds’ foraging effort. To reduce competition between the gannets and fisheries, the gannets’ core foraging areas seldomly overlapped with the fisheries catch locations, at the cost of the gannets’ increased foraging effort. One method to halt the Cape gannet population decline would be to conserve the fish resources close to the breeding colonies. This would reduce the birds’ foraging whereby increasing their fitness. Safeguarding small pelagic fish to ensure the perseverance of the remaining Benguela seabird populations, would lead to preserving the Benguela marine ecosystem as a whole. My study provided new insight into effects of fish stock management on Cape gannet foraging behaviour in South Africa, and the need for adequate management to ensure population persistence. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-12
- Authors: Strydom, Zanri , Grémillet, David , Pichegru, Lorien
- Date: 2023-12
- Subjects: Gannets -- South Africa , Birds of prey -- Behavior -- South Africa , Fish stock assessment
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/62622 , vital:72887
- Description: Seabirds are one of the most threatened groups of birds under both marine and terrestrial pressures. Among seabirds, the Cape gannet Morus capensis is a southern African endemic species facing several pressures of anthropogenic origin, including competition with industrial fisheries on small pelagic fish stocks. Cape gannets, being a long-lived species that is sensitive to environmental changes, are sentinels of change in oceanic environments granting it important to understand which factors influence their foraging behaviour and breeding outputs. For example, factors like age can result in a loss of physical capabilities which can lead to behavioral compensation and subsequent changes in chick provisioning rates and amounts. With the current fisheries management the fish stocks are continually decreasing, indicating the importance of an updated fine-scale assessment on the spatiotemporal overlap between foraging gannets and fisheries. The first objective of this thesis was to determine the influence of adult Cape gannets’ age and sex on their foraging characteristics and energy expenditure during foraging. I equipped chick-rearing Cape gannets of known age and sex with a 3D accelerometer and GPS device. Foraging effort (trip duration, foraging path and maximum distance to the nest) did not differ between sexes nor with age in Cape gannets. Both sexes rested less on the water with age. Aging females also spent more time in flight than males. The age- and sexual differences in energy expenditure prevalent in our study might reflect niche and/or risk partitioning strategies to ensure adequate provisioning to the chick. The second objective of this thesis was to determine the influence of fisheries catch rates, sardine and anchovy biomass, and adult foraging effort on chick growth rates in Cape gannets, using a long-term dataset collected between 2005 and 2020 on Malgas Island. I equipped chick-rearing adults with a GPS device and I weighed the chicks for between 3 to 6 increments to calculate the average daily mass increment. Of all the variables, foraging trip duration was the main determinant of daily growth rates, with chicks benefitting from parents’ shorter foraging trip durations. Chicks tended to grow slower when fisheries catch of sardine and anchovy were higher, possibly an effect of competition with fisheries. Chicks also grew faster when fish biomass was higher. This long-term monitoring demonstrated the possible effect of food competition between Cape gannets and fisheries, with negative impacts on gannet fitness as determined via chick growth rates. The third objective of this thesis was to determine the influence of both the biomass and fisheries catch rates of sardine and anchovy on Cape gannet foraging effort at a spatial and temporal scale. This was achieved by equipping a total of 668 chick-rearing Cape gannets with a GPS device. With an increase in fisheries catch there was an increase in the birds’ foraging effort. To reduce competition between the gannets and fisheries, the gannets’ core foraging areas seldomly overlapped with the fisheries catch locations, at the cost of the gannets’ increased foraging effort. One method to halt the Cape gannet population decline would be to conserve the fish resources close to the breeding colonies. This would reduce the birds’ foraging whereby increasing their fitness. Safeguarding small pelagic fish to ensure the perseverance of the remaining Benguela seabird populations, would lead to preserving the Benguela marine ecosystem as a whole. My study provided new insight into effects of fish stock management on Cape gannet foraging behaviour in South Africa, and the need for adequate management to ensure population persistence. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-12
Integrating state-space modelling and systematic conservation planning to recommend penguin-fishery management zones in Algoa Bay, South Africa
- Stockdale, Victoria, Goodall, Victoria, Clifford-Holmes, Jia
- Authors: Stockdale, Victoria , Goodall, Victoria , Clifford-Holmes, Jia
- Date: 2023-12
- Subjects: Biodiversity conservation -- South Africa -- Port Elizabeth , Natural resource conservation , Marine ecology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/62611 , vital:72828
- Description: Direct anthropogenic impacts on vulnerable marine ecosystems are growing and require effective conservation measures. Integrating the cost impacts of conservation interventions and optimising the spatiotemporal scale of management interventions may improve cohesion between opposing marine users. This study aimed to integrate spatial and temporal models to advise dynamic penguin-fishery management plans in Algoa Bay, off Gqeberha, South Africa, that would maximise penguin foraging success while minimising the impact on the fishing industry. Determining the foraging locations important to breeding penguins is fundamental when understanding the relationship between fisheries and prey availability. Using Global Positioning System (GPS) data gathered from feeding trips of breeding African penguins between 2012 and 2017, and a hidden Markov model, three behavioural states (foraging, commuting, transitioning) were inferred and used as conservation targets in spatial prioritisation using the prioritizr package in R. The cost to the fishery was estimated using the catch of pelagic fish by the fishing industry between 2012 and 2015 as the proxy. The energetic cost to penguins was the distance they travelled from their breeding colony. Nine prioritisation scenarios, varying in levels of conservation for penguins, spatial cohesion and costs to fisheries, were developed using all year’s combined data to explore an ‘optimal’ closure configuration. The optimal closure was determined as an area which met the targets for penguin conservation, with a low cost to the fishery, close to the breeding colony and spatially clumped. The best solution from each scenario was isolated and the solution for the conservation target of 20% foraging habitat, 10% commuting habitat and 10% transitioning habitat and a boundary penalty of 0.01 (a dimensionless value that is used to reduce spatial fragmentation – increasing the value of the parameter signals that it is important to minimise the total exposed boundary of the prioritisation by favouring solutions where units are clumped together) was chosen as the optimal closure. This configuration was used as a static closure and applied to individual fishing seasons to estimate how the cost of a static closure design to the fishery would vary between seasons. Subsequently, a dynamic closure was designed using the same optimal configuration criteria every year, and the cost to the fishing industry was compared seasonally with the cost of a static closure. The cost to fisheries of dynamic closures was consistently lower than that of a static closure and the area required to meet the penguin feeding targets was drastically reduced. While dynamic closure scenarios show promise to minimise costs to the industry while meeting penguin conservation targets, these configurations were designed retrospectively with data collected after the end of the fishery seasons. For efficient management, the closures need to be designed by using data collected at an appropriate temporal scale. For that, the critical missing dimension to this study is the addition of real-time data on pelagic fish positions, areas of fishing intensity and sites of penguin foraging to create appropriate recommendations for up-to-date fishery exclusion zones. Therefore, the priority now is to explore methods of collecting real-time data on pelagic fish abundance, feeding behaviour of penguins at sea, site and mass of pelagic fishery catch, and using these data to delineate real-time, dynamic closures, coupled with a governance and management strategy that can implement dynamic closures. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-12
- Authors: Stockdale, Victoria , Goodall, Victoria , Clifford-Holmes, Jia
- Date: 2023-12
- Subjects: Biodiversity conservation -- South Africa -- Port Elizabeth , Natural resource conservation , Marine ecology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/62611 , vital:72828
- Description: Direct anthropogenic impacts on vulnerable marine ecosystems are growing and require effective conservation measures. Integrating the cost impacts of conservation interventions and optimising the spatiotemporal scale of management interventions may improve cohesion between opposing marine users. This study aimed to integrate spatial and temporal models to advise dynamic penguin-fishery management plans in Algoa Bay, off Gqeberha, South Africa, that would maximise penguin foraging success while minimising the impact on the fishing industry. Determining the foraging locations important to breeding penguins is fundamental when understanding the relationship between fisheries and prey availability. Using Global Positioning System (GPS) data gathered from feeding trips of breeding African penguins between 2012 and 2017, and a hidden Markov model, three behavioural states (foraging, commuting, transitioning) were inferred and used as conservation targets in spatial prioritisation using the prioritizr package in R. The cost to the fishery was estimated using the catch of pelagic fish by the fishing industry between 2012 and 2015 as the proxy. The energetic cost to penguins was the distance they travelled from their breeding colony. Nine prioritisation scenarios, varying in levels of conservation for penguins, spatial cohesion and costs to fisheries, were developed using all year’s combined data to explore an ‘optimal’ closure configuration. The optimal closure was determined as an area which met the targets for penguin conservation, with a low cost to the fishery, close to the breeding colony and spatially clumped. The best solution from each scenario was isolated and the solution for the conservation target of 20% foraging habitat, 10% commuting habitat and 10% transitioning habitat and a boundary penalty of 0.01 (a dimensionless value that is used to reduce spatial fragmentation – increasing the value of the parameter signals that it is important to minimise the total exposed boundary of the prioritisation by favouring solutions where units are clumped together) was chosen as the optimal closure. This configuration was used as a static closure and applied to individual fishing seasons to estimate how the cost of a static closure design to the fishery would vary between seasons. Subsequently, a dynamic closure was designed using the same optimal configuration criteria every year, and the cost to the fishing industry was compared seasonally with the cost of a static closure. The cost to fisheries of dynamic closures was consistently lower than that of a static closure and the area required to meet the penguin feeding targets was drastically reduced. While dynamic closure scenarios show promise to minimise costs to the industry while meeting penguin conservation targets, these configurations were designed retrospectively with data collected after the end of the fishery seasons. For efficient management, the closures need to be designed by using data collected at an appropriate temporal scale. For that, the critical missing dimension to this study is the addition of real-time data on pelagic fish positions, areas of fishing intensity and sites of penguin foraging to create appropriate recommendations for up-to-date fishery exclusion zones. Therefore, the priority now is to explore methods of collecting real-time data on pelagic fish abundance, feeding behaviour of penguins at sea, site and mass of pelagic fishery catch, and using these data to delineate real-time, dynamic closures, coupled with a governance and management strategy that can implement dynamic closures. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-12
Foraging ecology of Kelp Gulls in natural and anthropogenically modified environments
- Authors: Reusch, Katharina
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/54106 , vital:46303
- Description: Humans are having a profound impact on the natural environment through a myriad of activities, such as land use change or direct exploitation of resources. Some species are able to adapt to these changes and thrive in deeply modified environments. They are often considered winners of global change. Among these are Kelp GullsLarus dominicanus in South Africa, which have a generalist foraging nature. Despite their abundance and potential role in the ecosystem, knowledge on their foraging ecology is limited, with no understanding of the role of natural and anthropogenic food resources during breeding. The aim of this thesis was to assess the foraging movements, diet and health of Kelp Gulls breeding in seven different colonies varying in proximity to landfills. GPS loggers were deployed on incubating adults to assess foraging trip patterns, effort, and habitats. Diet and trophic ecology of adults and chicks was determined during the breeding season by combining conventional diet analysis (i.e. stomach content samples and regurgitated pellets) with stable isotope analysis of blood plasma. Finally, population health was estimated using indices of body condition for adults and chicks, and blood and faecal parasites were examined. The first successful tracking data from Kelp Gulls in South Africa revealed that birds from all colonies spent more time foraging in natural environments (marine, coastal and terrestrial) than in anthropogenically modified ones, irrelevant of the distance to the nearest landfill, potentially reflecting prey profitability or availability around thebreeding colonies. Gulls also had higher foraging effort when foraging at sea (longer travelling distance), which might be balanced by foraging on high energy prey in themarine environment (e.g. fish). Diet and trophic ecology data confirmed the wide range of resources Kelp Gulls were capable of exploiting. Anthropogenic items were important food sources at some colonies, while annual differences in trophic level targeted were apparent at some other colonies, possibly reflecting varying predation levels on other seabirds. Diet and trophic ecology generally differed between adults and chicks, with chicks being fed a more marine, i.e. fish, and higher trophic level diet, potentially due to the higher energy content of fish being important for chick growth. Despite differences between colonies in foraging effort and diet, body condition of both adults and chicks was similar across colonies. Birds from one of the urban colonies, foraging at the local landfill, tended to have slightly higher body condition values, possibly due to the high fat content of anthropogenic items, although this was not significant. Blood parasites were very scarce, with only one genus identified, Haemoproteus spp. Parasite abundance was significantly lower in chicks than in adults, implicating that adults might get infected in areas outside the colony. Faecal smears revealed the presence of yeast cells (Candida spp.) in birds, coinciding with higher body condition values, possibly linked to foraging habitat choice, as birds might ingest yeast cells when feeding in urban areas contaminated with human excrement.Kelp Gulls breeding in South Africa forage on a wide variety of resources and habitats, with limited apparent impact on their parasite load and body condition. All colonies foraged to some extend on natural sources, although some colonies located in very urban areas seemed to depend more closely on anthropogenic items as food resource. Therefore, changes in e.g. landfill management might cause changes in population dynamics, with possible repercussions on neighbouring bird populations. Theirgeneralist foraging nature, among others, makes Kelp Gulls winners of global change and is partly responsible for their increased population numbers. As they are often perceived as pests, information on the foraging ecology is important to manage gull populations effectively. , Thesis (PhD) -- Faculty of Sciences, School of Environmental Sciences, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Reusch, Katharina
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/54106 , vital:46303
- Description: Humans are having a profound impact on the natural environment through a myriad of activities, such as land use change or direct exploitation of resources. Some species are able to adapt to these changes and thrive in deeply modified environments. They are often considered winners of global change. Among these are Kelp GullsLarus dominicanus in South Africa, which have a generalist foraging nature. Despite their abundance and potential role in the ecosystem, knowledge on their foraging ecology is limited, with no understanding of the role of natural and anthropogenic food resources during breeding. The aim of this thesis was to assess the foraging movements, diet and health of Kelp Gulls breeding in seven different colonies varying in proximity to landfills. GPS loggers were deployed on incubating adults to assess foraging trip patterns, effort, and habitats. Diet and trophic ecology of adults and chicks was determined during the breeding season by combining conventional diet analysis (i.e. stomach content samples and regurgitated pellets) with stable isotope analysis of blood plasma. Finally, population health was estimated using indices of body condition for adults and chicks, and blood and faecal parasites were examined. The first successful tracking data from Kelp Gulls in South Africa revealed that birds from all colonies spent more time foraging in natural environments (marine, coastal and terrestrial) than in anthropogenically modified ones, irrelevant of the distance to the nearest landfill, potentially reflecting prey profitability or availability around thebreeding colonies. Gulls also had higher foraging effort when foraging at sea (longer travelling distance), which might be balanced by foraging on high energy prey in themarine environment (e.g. fish). Diet and trophic ecology data confirmed the wide range of resources Kelp Gulls were capable of exploiting. Anthropogenic items were important food sources at some colonies, while annual differences in trophic level targeted were apparent at some other colonies, possibly reflecting varying predation levels on other seabirds. Diet and trophic ecology generally differed between adults and chicks, with chicks being fed a more marine, i.e. fish, and higher trophic level diet, potentially due to the higher energy content of fish being important for chick growth. Despite differences between colonies in foraging effort and diet, body condition of both adults and chicks was similar across colonies. Birds from one of the urban colonies, foraging at the local landfill, tended to have slightly higher body condition values, possibly due to the high fat content of anthropogenic items, although this was not significant. Blood parasites were very scarce, with only one genus identified, Haemoproteus spp. Parasite abundance was significantly lower in chicks than in adults, implicating that adults might get infected in areas outside the colony. Faecal smears revealed the presence of yeast cells (Candida spp.) in birds, coinciding with higher body condition values, possibly linked to foraging habitat choice, as birds might ingest yeast cells when feeding in urban areas contaminated with human excrement.Kelp Gulls breeding in South Africa forage on a wide variety of resources and habitats, with limited apparent impact on their parasite load and body condition. All colonies foraged to some extend on natural sources, although some colonies located in very urban areas seemed to depend more closely on anthropogenic items as food resource. Therefore, changes in e.g. landfill management might cause changes in population dynamics, with possible repercussions on neighbouring bird populations. Theirgeneralist foraging nature, among others, makes Kelp Gulls winners of global change and is partly responsible for their increased population numbers. As they are often perceived as pests, information on the foraging ecology is important to manage gull populations effectively. , Thesis (PhD) -- Faculty of Sciences, School of Environmental Sciences, 2021
- Full Text:
- Date Issued: 2021-12
Behavioural flexibility in an endangered seabird during current changes
- Authors: Traisnel, Gwendoline
- Date: 2019
- Subjects: Penguins -- South Africa , Penguins -- Behavior Sea birds -- Behavior Sea birds -- Ecology
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/43800 , vital:37048
- Description: Penguins spend a large part of their life cycle at sea and are amongst the most threatened seabirds as they suffer high mortality and have low reproductive success. Across the world, many populations are currently declining despite the constant development of conservation actions. The lack of information at the individual level reduces the understanding of individual variability and its potential role in the population dynamics of these vulnerable species. For example, long-lived species are characterised by substantial individual heterogeneity in their contribution to the overall population dynamic that should be understood when considering the implemention of conservation policies. This thesis explored some of the primary mechanisms behind inter-individual differences in behaviour and breeding success in the endangered African penguin Spheniscus demersus. On Bird island (Algoa Bay), nest defence behaviours were investigated on adults brooding chicks 1-3 weeks-old and chicks were measured at regular intervals (every 5 days) to assess their growth rate, a proxy for breeding success in this species. All adults were sexed and implanted with a passive integrated transponder which was used for individual identification. In this species, males are usually larger than females and have a higher survival rates both as juveniles and as adults. A subsample of them was equipped with tracking devices (GPSs and Time Depth Recorders), sometimes over consecutive foraging trips and across years. Finally, mate and nest fidelity were investigated to understand the drivers and consequences of this trait in that population. Breeding success was linked to nest defence behaviours, with bolder birds generally showing lower breeding success. This relation could not, however, be explained by differences in foraging strategies. Males were generally bolder than females when defending the nests, but their foraging behaviour did not vary with their personality. They generally had lower foraging effort than females. By contrast, bolder females performed more sinuous path, more wiggles and travelled larger vertical distances than shyer ones. Overall, females were more flexible than males over consecutive trips, suggesting that they probably adjust their behaviours to the offspring needs in this species. However, no sex difference in behavioural flexibility between sexes was visible across years, indicating that environmental variability may equally impact females and males’ behaviour over such time-scale. Generally, consistency was time-scale dependent as penguins increased their foraging flexibility across years, potentially adjusting to the variability of the environment. Interestingly, foraging consistency over consecutive trips increased during years of poor environmental conditions, and individuals with consistent foraging strategies were more successful than more flexible individuals when resources were extremely scarce. Finally, while nest and mate fidelity were high in this species, individuals that changed nest/partners, improved their breeding outcome. Particularly, after low breeding success females were more likely to change nest site and thereby partner to possibly improve their fitness. The potential biased adult sex ratio towards males in this population may facilitate changes in females which may have more partners available to re-mate than males. The present thesis reveals the existence of individual differences in behaviour and breeding success which relate to personality in penguins. These findings highlight the importance to integrate individual variability to predict future population dynamics in the context of global changes to understand the resilience and vulnerability of the species.
- Full Text:
- Date Issued: 2019
- Authors: Traisnel, Gwendoline
- Date: 2019
- Subjects: Penguins -- South Africa , Penguins -- Behavior Sea birds -- Behavior Sea birds -- Ecology
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/43800 , vital:37048
- Description: Penguins spend a large part of their life cycle at sea and are amongst the most threatened seabirds as they suffer high mortality and have low reproductive success. Across the world, many populations are currently declining despite the constant development of conservation actions. The lack of information at the individual level reduces the understanding of individual variability and its potential role in the population dynamics of these vulnerable species. For example, long-lived species are characterised by substantial individual heterogeneity in their contribution to the overall population dynamic that should be understood when considering the implemention of conservation policies. This thesis explored some of the primary mechanisms behind inter-individual differences in behaviour and breeding success in the endangered African penguin Spheniscus demersus. On Bird island (Algoa Bay), nest defence behaviours were investigated on adults brooding chicks 1-3 weeks-old and chicks were measured at regular intervals (every 5 days) to assess their growth rate, a proxy for breeding success in this species. All adults were sexed and implanted with a passive integrated transponder which was used for individual identification. In this species, males are usually larger than females and have a higher survival rates both as juveniles and as adults. A subsample of them was equipped with tracking devices (GPSs and Time Depth Recorders), sometimes over consecutive foraging trips and across years. Finally, mate and nest fidelity were investigated to understand the drivers and consequences of this trait in that population. Breeding success was linked to nest defence behaviours, with bolder birds generally showing lower breeding success. This relation could not, however, be explained by differences in foraging strategies. Males were generally bolder than females when defending the nests, but their foraging behaviour did not vary with their personality. They generally had lower foraging effort than females. By contrast, bolder females performed more sinuous path, more wiggles and travelled larger vertical distances than shyer ones. Overall, females were more flexible than males over consecutive trips, suggesting that they probably adjust their behaviours to the offspring needs in this species. However, no sex difference in behavioural flexibility between sexes was visible across years, indicating that environmental variability may equally impact females and males’ behaviour over such time-scale. Generally, consistency was time-scale dependent as penguins increased their foraging flexibility across years, potentially adjusting to the variability of the environment. Interestingly, foraging consistency over consecutive trips increased during years of poor environmental conditions, and individuals with consistent foraging strategies were more successful than more flexible individuals when resources were extremely scarce. Finally, while nest and mate fidelity were high in this species, individuals that changed nest/partners, improved their breeding outcome. Particularly, after low breeding success females were more likely to change nest site and thereby partner to possibly improve their fitness. The potential biased adult sex ratio towards males in this population may facilitate changes in females which may have more partners available to re-mate than males. The present thesis reveals the existence of individual differences in behaviour and breeding success which relate to personality in penguins. These findings highlight the importance to integrate individual variability to predict future population dynamics in the context of global changes to understand the resilience and vulnerability of the species.
- Full Text:
- Date Issued: 2019
Involving fishermen in seabirds’ conservation: bridging the gap between socio-economic needs of industry and the needs of seabirds
- Authors: Ginsburg, Tayla
- Date: 2019
- Subjects: Sea birds -- Ecology , Island ecology Island animals -- Conservation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/42184 , vital:36633
- Description: Marine ecosystems and species face multiple threats, particularly intensive industrial-scale fishing activities. As the human population continues to increase exponentially and drive a greater demand for food, commercial fishing effort will likely intensify. While terrestrial protected areas are well developed, marine protected areas (MPAs) are less so, both in the area covered and management practices. There is currently a drive to increase the extent of MPAs, both globally and in South Africa, particularly for those ecosystems and marine species that can benefit from area-based management. The size, shape, location zonation of MPAs generally remain static through time. However, the ocean is a dynamic environment and static MPAs are not always able to achieve conservation objectives for their component ecosystems and species. Dynamic Ocean Management (DOM) is an approach that integrates near real-time data on biological, oceanographic, social and/or economic variables to adjust an MPAs boundary and zonation in both space and time. The aim of this thesis was to assess the viability of applying DOM to a fishing exclusion zone within a zoned MPA in Algoa Bay, South Africa, to support conservation objectives for the Endangered African penguin Spheniscus demersus. Algoa Bay supports half of the world’s remaining population of this species. First, the degree of spatial overlap between foraging penguins and purse-seine fishers in Algoa Bay was determined over five years. In all years, purse-seiner fishing vessels were located around or near to St Croix Island and a large proportion of the total pelagic fish catch from the Bay was removed from this area. Breeding penguins travelled significantly further while foraging when the overlap (and subsequent competition for pelagic fish) was higher, suggesting that African penguins would benefit from a fishing exclusion zone around St Croix Island owing to reduced competition. However, an exclusion zone can have socio-economic impacts on fisheries as a result of the lost fishing area. A common concern raised by fishers is the direct loss of income, either as a result of increased fuel costs to reach alternate fishing grounds or decreased catch. An analysis of catch and travel time (as a proxy for fuel costs) when a 20 km exclusion zone was present or absent around St Croix Island revealed that the exclusion zone scenarios had no significant impact on either variable. Interviews with individuals in the local purse-seine fishery (both fishers and factory managers) showed a consensus that the marine environment needs protection and that MPAs have various environmental benefits. Despite this, individuals were concerned about how they would be impacted by the exclusion zone in the MPA. The interviews highlighted the willingness of individuals in the purse-seine fishery to talk to and work with scientists.
- Full Text:
- Date Issued: 2019
- Authors: Ginsburg, Tayla
- Date: 2019
- Subjects: Sea birds -- Ecology , Island ecology Island animals -- Conservation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/42184 , vital:36633
- Description: Marine ecosystems and species face multiple threats, particularly intensive industrial-scale fishing activities. As the human population continues to increase exponentially and drive a greater demand for food, commercial fishing effort will likely intensify. While terrestrial protected areas are well developed, marine protected areas (MPAs) are less so, both in the area covered and management practices. There is currently a drive to increase the extent of MPAs, both globally and in South Africa, particularly for those ecosystems and marine species that can benefit from area-based management. The size, shape, location zonation of MPAs generally remain static through time. However, the ocean is a dynamic environment and static MPAs are not always able to achieve conservation objectives for their component ecosystems and species. Dynamic Ocean Management (DOM) is an approach that integrates near real-time data on biological, oceanographic, social and/or economic variables to adjust an MPAs boundary and zonation in both space and time. The aim of this thesis was to assess the viability of applying DOM to a fishing exclusion zone within a zoned MPA in Algoa Bay, South Africa, to support conservation objectives for the Endangered African penguin Spheniscus demersus. Algoa Bay supports half of the world’s remaining population of this species. First, the degree of spatial overlap between foraging penguins and purse-seine fishers in Algoa Bay was determined over five years. In all years, purse-seiner fishing vessels were located around or near to St Croix Island and a large proportion of the total pelagic fish catch from the Bay was removed from this area. Breeding penguins travelled significantly further while foraging when the overlap (and subsequent competition for pelagic fish) was higher, suggesting that African penguins would benefit from a fishing exclusion zone around St Croix Island owing to reduced competition. However, an exclusion zone can have socio-economic impacts on fisheries as a result of the lost fishing area. A common concern raised by fishers is the direct loss of income, either as a result of increased fuel costs to reach alternate fishing grounds or decreased catch. An analysis of catch and travel time (as a proxy for fuel costs) when a 20 km exclusion zone was present or absent around St Croix Island revealed that the exclusion zone scenarios had no significant impact on either variable. Interviews with individuals in the local purse-seine fishery (both fishers and factory managers) showed a consensus that the marine environment needs protection and that MPAs have various environmental benefits. Despite this, individuals were concerned about how they would be impacted by the exclusion zone in the MPA. The interviews highlighted the willingness of individuals in the purse-seine fishery to talk to and work with scientists.
- Full Text:
- Date Issued: 2019
Penguin parenting : assortative mating, nest attendance and sex-specific chick provisioning in the African Penguin (Spheniscus demersus)
- Authors: Smith, Diane Lauren
- Date: 2016
- Subjects: African penguin , Penguins -- South Africa , Penguins -- Sexual behavior , Parental behavior in animals
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5943 , http://hdl.handle.net/10962/d1019993
- Description: Animal behaviour is especially sensitive to environmental variability and prey availability during the breeding season, and this is particularly true for non-volant, central place foragers such as the endangered African Penguin (Spheniscus demersus). Individual sex and morphology, as well as the level of assortment within mated pairs can influence both the behaviour and the reproductive success of species exhibiting biparental care. This study made use of a large biometric database and nest attendance video footage to determine the influence of intrinsic (assortative mating, brood size and chick age) and extrinsic (environmental conditions, anthropic disturbance) factors on breeding behaviour and performance of African Penguins on Bird Island, Algoa Bay, during peak breeding (March - July) in 2013. While sexual dimorphism in African Penguins is subtle, the colony-specific discriminant functions presented here provide an accurate sexing tool when only bill and flipper length are available. Despite the premise that selection of a large, high-quality mate in this longlived, monogamous seabird governs lifetime fitness, only low levels of assortative mating were found, and this only for earlier breeders, when larger females (but not males) bred. The 2013 season was a particularly successful one, coinciding with above-average sardine and anchovy abundance, and almost 80 percent of monitored nests were double-brooded, with very low levels of mortality. A- and B-chicks of double broods and singleton chicks grew at similar rates and exhibited similar body condition indices. In these conditions, chick developmental rates were independent of parental size, assortment or provisioning behaviour. Females raising a double brood were significantly lighter and in poorer body condition than those raising a single chick, although the same trend was not evident in males. Offspring sex ratio in 2013 (2.27:1) favoured male chicks, suggesting that there is potential to over-produce the larger sex when resources are plentiful. Peak nest arrival and departure times of parents did not change over the course of monitored breeding attempts (March-June), nor were they different for disturbed and undisturbed nests or for a single or double brood. The increase in CCTV-observed provisioning rate as chicks grew larger was best explained by brood size, at-sea chlorophyll a concentration, and maximum air temperature, but was unrelated to parental morphology or assortative index. Importantly, parental absenteeism commenced earlier and was markedly greater in nests frequently handled by researchers than in undisturbed nests. Both the time spent together by parents, and absenteeism were measurably affected by maximum afternoon air temperatures, the effects of which are expected to be exacerbated by poorer foraging conditions and climate change. A third of manually-monitored nests shared chick-guarding duties unequally, although this phenomenon was independent of parental sex or morphology. The adaptive benefits of mating patterns and division of labour during chick-rearing may only become apparent in a year of below-average food availability and it is highly recommended that this study be repeated in a year of scarce food resources. These findings augment past foraging ecology studies and demonstrate that investigator disturbance and environmental conditions can affect the nesting behaviour of this highly threatened seabird.
- Full Text:
- Date Issued: 2016
- Authors: Smith, Diane Lauren
- Date: 2016
- Subjects: African penguin , Penguins -- South Africa , Penguins -- Sexual behavior , Parental behavior in animals
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5943 , http://hdl.handle.net/10962/d1019993
- Description: Animal behaviour is especially sensitive to environmental variability and prey availability during the breeding season, and this is particularly true for non-volant, central place foragers such as the endangered African Penguin (Spheniscus demersus). Individual sex and morphology, as well as the level of assortment within mated pairs can influence both the behaviour and the reproductive success of species exhibiting biparental care. This study made use of a large biometric database and nest attendance video footage to determine the influence of intrinsic (assortative mating, brood size and chick age) and extrinsic (environmental conditions, anthropic disturbance) factors on breeding behaviour and performance of African Penguins on Bird Island, Algoa Bay, during peak breeding (March - July) in 2013. While sexual dimorphism in African Penguins is subtle, the colony-specific discriminant functions presented here provide an accurate sexing tool when only bill and flipper length are available. Despite the premise that selection of a large, high-quality mate in this longlived, monogamous seabird governs lifetime fitness, only low levels of assortative mating were found, and this only for earlier breeders, when larger females (but not males) bred. The 2013 season was a particularly successful one, coinciding with above-average sardine and anchovy abundance, and almost 80 percent of monitored nests were double-brooded, with very low levels of mortality. A- and B-chicks of double broods and singleton chicks grew at similar rates and exhibited similar body condition indices. In these conditions, chick developmental rates were independent of parental size, assortment or provisioning behaviour. Females raising a double brood were significantly lighter and in poorer body condition than those raising a single chick, although the same trend was not evident in males. Offspring sex ratio in 2013 (2.27:1) favoured male chicks, suggesting that there is potential to over-produce the larger sex when resources are plentiful. Peak nest arrival and departure times of parents did not change over the course of monitored breeding attempts (March-June), nor were they different for disturbed and undisturbed nests or for a single or double brood. The increase in CCTV-observed provisioning rate as chicks grew larger was best explained by brood size, at-sea chlorophyll a concentration, and maximum air temperature, but was unrelated to parental morphology or assortative index. Importantly, parental absenteeism commenced earlier and was markedly greater in nests frequently handled by researchers than in undisturbed nests. Both the time spent together by parents, and absenteeism were measurably affected by maximum afternoon air temperatures, the effects of which are expected to be exacerbated by poorer foraging conditions and climate change. A third of manually-monitored nests shared chick-guarding duties unequally, although this phenomenon was independent of parental sex or morphology. The adaptive benefits of mating patterns and division of labour during chick-rearing may only become apparent in a year of below-average food availability and it is highly recommended that this study be repeated in a year of scarce food resources. These findings augment past foraging ecology studies and demonstrate that investigator disturbance and environmental conditions can affect the nesting behaviour of this highly threatened seabird.
- Full Text:
- Date Issued: 2016
Influence of anthropogenic stressors on the behaviour and mortality of the endangered African penguin
- Authors: Nyengera, Reason
- Date: 2014
- Subjects: African penguin -- South Africa -- Algoa Bay , Birds -- Mortality -- South Africa -- Algoa Bay , Endangered species -- Breeding -- South Africa -- Algoa Bay
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3064 , vital:20395
- Description: This study investigated the potential impacts of several anthropogenic stressors on the movement and survival of African penguins in Algoa Bay, taking into account prey availability and environmental conditions (sea surface temperature and chlorophyll productivity). The primary drive for the study was based on the seismic exploration, which took place in the habitat of the endangered African penguin. The research was also carried out to understand how pelagic fishing and prey availability influence the broader behavioural and mortality aspects of penguins. To achieve this goal, I used monthly beach surveys to assess seabird mortality, admissions of penguins in rehabilitation centres and the monitoring of breeding penguins’ movement at sea through individual GPS tracking. In addition, prey distribution and abundance were monitored with acoustic surveys to assess potential changes in relation anthropogenic stressors. Breeding African penguins did not react dramatically to seismic activities, except on St Croix Island where they changed their foraging direction during the seismic period. There was no evidence of a siginficant increase in African penguin carcasses encountered or strandings along the beaches during the period of seismic activity. However, a sharp increase in encounter rate was recorded soon after seismic operations, which may potentially indicate a delay between the effect of seismic activities on penguin mortality and the encounter of the related carcasses after the operation. However, the impact of seismic surveys on penguins may be long-term rather than short term, and additional studies would be needed to reveal long-term effects of seismic activities, if any. Foraging effort of breeding African penguins increased substantially in the presence of commercial fishing activities within close proximity to the colonies. To a greater extent, at-sea movement patterns and counts of beach cast carcasses were largely influenced by prey availability. Penguins spent more time at sea, traveled longer and covered a larger foraging area during periods of relatvely low pelagic fish abundance. There was also a sharp increase in African penguin mortality during periods of low prey availability in the Bay. However, environmental conditions showed some influence over these interactions. Foraging effort of breeding African penguins increased substantially in the presence of commercial fishing activities within close proximity to the colonies. To a greater extent, at-sea movement patterns and counts of beach cast carcasses were largely influenced by prey availability. Penguins spent more time at sea, traveled longer and covered a larger foraging area during periods of relatvely low pelagic fish abundance. There was also a sharp increase in African penguin mortality during periods of low prey availability in the Bay. However, environmental conditions showed some influence over these interactions. For example a red tide event during in period of low prey availability, made it difficult to understand impacts of prey on penguins difficult. Both anthropogenic stressors and environmental conditions influenced African penguins’ behaviour and survival. Due to the worrying trend of African penguins in South Africa for the past few years, all conservation management efforts to increase penguin numbers and limit their mortality are necessary. This study highlights the negative impact of industrial fishing on this Endangered species and the rapid increase in mortality of penguins during times of low prey availability. A network of Marine Protected Areas would certainly increase food availability to African penguins by limiting competition with fisheries, and contribute to increasing the population numbers.
- Full Text:
- Date Issued: 2014
- Authors: Nyengera, Reason
- Date: 2014
- Subjects: African penguin -- South Africa -- Algoa Bay , Birds -- Mortality -- South Africa -- Algoa Bay , Endangered species -- Breeding -- South Africa -- Algoa Bay
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3064 , vital:20395
- Description: This study investigated the potential impacts of several anthropogenic stressors on the movement and survival of African penguins in Algoa Bay, taking into account prey availability and environmental conditions (sea surface temperature and chlorophyll productivity). The primary drive for the study was based on the seismic exploration, which took place in the habitat of the endangered African penguin. The research was also carried out to understand how pelagic fishing and prey availability influence the broader behavioural and mortality aspects of penguins. To achieve this goal, I used monthly beach surveys to assess seabird mortality, admissions of penguins in rehabilitation centres and the monitoring of breeding penguins’ movement at sea through individual GPS tracking. In addition, prey distribution and abundance were monitored with acoustic surveys to assess potential changes in relation anthropogenic stressors. Breeding African penguins did not react dramatically to seismic activities, except on St Croix Island where they changed their foraging direction during the seismic period. There was no evidence of a siginficant increase in African penguin carcasses encountered or strandings along the beaches during the period of seismic activity. However, a sharp increase in encounter rate was recorded soon after seismic operations, which may potentially indicate a delay between the effect of seismic activities on penguin mortality and the encounter of the related carcasses after the operation. However, the impact of seismic surveys on penguins may be long-term rather than short term, and additional studies would be needed to reveal long-term effects of seismic activities, if any. Foraging effort of breeding African penguins increased substantially in the presence of commercial fishing activities within close proximity to the colonies. To a greater extent, at-sea movement patterns and counts of beach cast carcasses were largely influenced by prey availability. Penguins spent more time at sea, traveled longer and covered a larger foraging area during periods of relatvely low pelagic fish abundance. There was also a sharp increase in African penguin mortality during periods of low prey availability in the Bay. However, environmental conditions showed some influence over these interactions. Foraging effort of breeding African penguins increased substantially in the presence of commercial fishing activities within close proximity to the colonies. To a greater extent, at-sea movement patterns and counts of beach cast carcasses were largely influenced by prey availability. Penguins spent more time at sea, traveled longer and covered a larger foraging area during periods of relatvely low pelagic fish abundance. There was also a sharp increase in African penguin mortality during periods of low prey availability in the Bay. However, environmental conditions showed some influence over these interactions. For example a red tide event during in period of low prey availability, made it difficult to understand impacts of prey on penguins difficult. Both anthropogenic stressors and environmental conditions influenced African penguins’ behaviour and survival. Due to the worrying trend of African penguins in South Africa for the past few years, all conservation management efforts to increase penguin numbers and limit their mortality are necessary. This study highlights the negative impact of industrial fishing on this Endangered species and the rapid increase in mortality of penguins during times of low prey availability. A network of Marine Protected Areas would certainly increase food availability to African penguins by limiting competition with fisheries, and contribute to increasing the population numbers.
- Full Text:
- Date Issued: 2014
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