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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
131

Patterns in reef fish assemblages as determined by baited remote underwater video (BRUV) along the western side of False Bay: effects of site, depth and protection status

Sanguinetti, Carolyn Anna Victoria January 2013 (has links)
Includes bibliographical references. / By protecting ecosystems from exploitation, no-take zones are considered the principal means by which marine species and their populations can be conserved for future generations. To be successful, no-take zones require continuous monitoring of the fish community to evaluate the response of marine ecosystems to anthropogenic impacts and environmental change. Obtaining an understanding of the patterns of species composition, abundance, and distribution, allows monitoring efforts to be focused, efficient, and properly interpreted. Baited remote underwater video (BRUV) was used to examine the effects of site, depth, andlevel of protection, on the diversity and relative abundance of temperate reef fish within the Table Mountain National Park (TMNP) Marine Protected Area (MPA). Four notake zones and adjacent exploited areas, subject to conventional management restrictions, were sampled monthly over a four-month period. A total of 36 species from three marine classes and 18 families was recorded. Species diversity (Shannon-Wiener index) was found to increase with sites closest to the mouth of the bay, whilst species abundance was found to increase with depth. Results indicated no consistent response to protection status among the sites at either the community or individual species level. However, the oldest no-take zone proclaimed for the purposes of reef conservation was found to harbour higher species diversity and a higher relative abundance of fish compared to its respective exploited area. Furthermore, the similar frequencies in which hottentot (Pachymetopon blochii) and roman (Chrysoblephus laticeps) were observed across the four study sites, suggests that these two commercially-important species are successfully recruiting inside and outside the no-take zones. These results indicate that physical factors, rather than protection status, within False Bay influence patterns of fish assemblage composition, abundance, and distribution. In future, and to improve comparability, assessments within the TMNP MPA should be designed to target similar locations and depth ranges within the bay. The success of no-take zones must be evaluated according to their individual design and management goals.
132

Evaluating a citizen science research programme : understanding the people who make it possible

Wright, Dale January 2011 (has links)
Includes abstract. / Includes bibliographical references (p. 99-110). / Citizen science is increasingly recognised as a useful tool for conducting scientific research and public outreach, producing multiple positive benefits for biodiversity conservation and the volunteers involved in such research.
133

Is the grass really greener on the other side?

Lane, Wade Howard January 2013 (has links)
While many studies focus on identifying pollutants within an ecosystem or how they affect primary producers, few look at how pollutants move through trophic levels or their influence on animal demography. The aim of this study was to determine whether additional nitrogen, phosphorus and water, to a savanna would alter the vegetation quality enough to influence the feeding behaviour and diet of the ungulate populations both of which would alter the vegetation quantity. The study was conducted in the Kruger National Park. One site was supplied with additional nutrients and compared to three control sites. The nitrogen and phosphorus content of grass and tree leaves collected at the enriched site were higher than the leaves collected at the control site, indicating the additional nutrients are improving the vegetation quality. Feeding rates (determined from photos captured by camera traps) indicated a higher degree of herbivory at the enriched site. However, there was no difference in the δ¹³C value, nitrogen and phosphorus content in the ungulate dung collected amongst the study sites suggesting no change in the diet. The dominant grass was significantly shorter at the enriched site suggesting that increased grazing was diminishing grass biomass. Basic assessment of the trees indicated that the additional water at the enriched site seemed to be triggering an earlier start to the growing season for the trees. It was concluded that the additional nutrients have altered the vegetation structure enough to potentially influence animal demographics.
134

Remotely operated vehicle exploring ichthyofauna association with habitat from shore-shelf, in an endemism hotspot in South Africa

Button, Rio E 08 February 2019 (has links)
The priority of understanding marine systems increases as expanding pressures are exerted on them. In South Africa, efforts are underway to utilise the ocean to stimulate economic growth which will result in further pressures on marine systems. The aim is to mitigate pressures, largely through proposed offshore marine protected areas (MPAs). One of these proposed MPAs is situated off the Kei river mouth in the Eastern Cape of South Africa. The area offshore of the Kei river mouth is an endemism hotspot, and a transitional zone between the Subtropical East Coast and the Warm Temperate South Coast. The region waslargely unexplored because of itstreacherous sea conditions and because it was no longer an area of commercial fishing importance. A remotely operated vehicle (ROV) explored the regions’ fish and benthic habitats and investigated their associations. This study’s results provide quantitative information on fish and habitat diversity in the intermediate depths off the Kei river mouth. Observations of rare, commercially important, yet critically endangered charismatic reef fish species were made. These included red steenbras (Petrus Rupestris), seventy-four (Polysteganus undulosus), red stumpnose (Chrysoblephus gibbiceps) and dageraad (Chrysoblephus cristiceps). Habitat types, including rhodolith beds, sponges, and deep-water corals were documented. Maximum predicted fish diversity corresponded with mid-continental shelf, which is incorporated into the regions proposed MPA. The highest fish diversity was 10km within the shelf edge (which had a depth of approximately 100m) and was associated with the most structurally complex habitat biota: Fan Coral. Depth was a fundamental predictor associated with the presence and abundance of species distributions. The results support the location of the proposed MPA and are a step forward in identifying critical habitat to protect diversity and endangered species, and thus contribute to the regions spatial management and governance.
135

Effects of fire frequency and seasonality on the population dynamics of the critically endangered Clanwilliam cedar

Ncube, Thinabakho R. L. 27 January 2020 (has links)
The Clanwilliam cedar, (Widdringtonia wallichii, formerly W. cedarbergensis) is a threatened conifer endemic to the fire-adapted fynbos vegetation of the Cederberg mountains, South Africa. Here its population size has drastically declined, and its conservation status subsequently escalated to critically endangered in 2013 by IUCN Red List of Plants. Studies have hypothesised that excessive exploitation for timber products, climate change and unfavourable fire regimes (frequency, intensity and season) have contributed to this species’ decline. This decline led to the overarching aim of the study to gain a better understanding of the effects of fire frequency and seasonality on the life history of Clanwilliam cedar. To characterise fire patterns in the Cederberg Wilderness Area, I used a latent class analysis on fire indices calculated from a fire history database. To explore the effects of fire seasonality on the cedar count numbers I used a negative binomial hurdle model using seasonal fire indices and environmental data. To examine the impact of fire frequency and seasonality on the life-history of the Clanwilliam cedar, I used a stochastic demographic model based on parameter values obtained from the literature. Findings from the latent class model indicated that the main axes of variation in fire frequency were the fire indices representing total fire frequency, summer fires, autumn fires in the last 30 years and fires in the last 30 years. Although these fire indices were able to distinguish relatively well between the three latent classes, it however was difficult to disentangle the relative importance of each fire index due to their strong covariation. This points to a more general pattern, suggesting that it is necessary to examine the entire fire frequency history and the seasonality pattern in order to understand the current state of the population of the Clanwilliam cedar. The linear count model revealed autumn fires as being positively associated, whereas mean annual precipitation and mean annual temperature and precipitation seasonality were negatively associated with the cedar numbers. The stochastic demographic model showed both summer and winter fires induce positive growth rates at firereturn intervals greater than 10 years, but winter fires always permitted a higher population growth rate. The sensitivity analysis of the stochastic population growth rate (log λs) to changes in the life-history parameters at fire-return intervals of 10 and 20 years showed that fire mortality was most important for a summer fire regime, and growth rates of adult trees were most important for a winter fire regime. The different methods used in this study provided different but complementary results, and thus insights from these various models could potentially contribute to the development of fire management strategies that reflect the complexities of fire frequency and seasonality on the population dynamics and thus persistence of the Clanwilliam cedar.
136

Major histocompatibility complex diversity in an urban Chacma baboon (Papio ursinus) population: Implications for conservation

McCarter, Jenneca M January 2012 (has links)
Includes abstract. / Includes bibliographical references. / Since the 15th century, human activity has altered and degraded nearly half of the available land of the Cape Peninsula, South Africa; this has resulted in significant restriction and fragmentation of the historic geographic range of the peninsula's Chacma baboon (Papio ursinus) population.
137

The role of buoyancy in the dispersal of marine plastic debris and the impact of biofouling : does size matter?

Fazey, Francesca Margaret Catherine January 2015 (has links)
Recent studies suggest that a significant proportion of the plastic pollution that enters the sea is disappearing from the surface, despite being less dense than seawater. Observations across size classes show that it is particularly smaller plastics, <5 mm in length, that are susceptible to removal. The dynamics and transport mechanisms that determine the pathways taken by floating marine plastic debris are poorly understood and the processes causing this disappearance of plastic are unknown. A spatial gradient in the size composition of floating litter has also recently been observed by visual at-sea surveys in the South Atlantic Ocean, where smaller plastic litter items are found in greater relative abundance closer to the coast becoming less frequent with increasing distance out to sea. Conversely, larger, more buoyant plastic items were found to be proportionally more abundant at greater distances away from the coastal source. Both the observations of missing microplastic and the apparent spatial gradient evident in the size composition of dispersing litter suggest that size selective mechanisms are removing smaller fragments of plastics from the surface. The nature of these and the whereabouts and ultimate fate of these smaller plastic fragments is unknown. Two studies were conducted. The first was an empirical investigation to confirm how the size and buoyancy of litter items are influenced by dispersal distances from a point source. Beach littler samples were collected from beaches at increasing distances from a major pollution source: Cape Town in the Western Cape province of South Africa. The size and buoyancy compositions of litter at each distance interval were compared. Mean size and buoyancy increased significantly with increased distance from Cape Town. Mean item volume rose from 5.1 ml to 604 ml. Over 90% of the items recovered closer to Cape Town were in the two lowest buoyancy categories, in contrast to the furthest sampling site, where only 20% of the litter recovered occupied these categories and 55% occupied higher bin ranges. The findings from the beach litter samples were comparable to those of the recent at-sea surveys in the same region and confirmed the spatial gradient in size composition shown by that study. The second study was an experimental investigation into marine biofouling as a possible explanation for the size-selective sinking of smaller plastics at sea. . The study was conducted in situ at the False Bay Yacht Club in Simon's Town in the Western Cape. Samples of highdensity and low-density polyethylene plastic of varying thickness were cut into squares of three different sizes, tethered to exposure rails and submerged approximately 10 cm below the surface for a 12-week study period. A subset was removed bi-weekly, their buoyancy observed and change in dry weight measured. My results showed that both fragment size and material thickness were significant determinants of fouling mass accumulated. Exposure times required for sinking varied from 17 days for the smallest thinnest samples to 66 days for the largest, thickest ones. All sample sizes sank within the study period. Sample volume was a close correlate of time to sinking. Refined versions of these estimates could be scaled by factors such as environmental conditions and proximity to litter inputs, and potentially included into numerical models of floating litter abundance and distribution. Both studies showed that high volume debris items persist longer at the ocean surface.
138

Changes in nesting numbers and breeding success of African White-backed Vultures in northern Botswana

Leepile, Leungo Boikanyo L 21 February 2019 (has links)
African White-backed Vultures have recently been uplisted to Critically Endangered by the IUCN due to declines across their range mainly linked to high levels of poisoning. Botswana likely supports significant numbers of this species, but as yet there is no published information on their population trends or their breeding success in this country. However, in recent years within Botswana and neighbouring countries there have been multiple incidents of mass poisonings, which have resulted in the deaths of thousands of White-backed Vultures. I therefore expected that nesting numbers of this species may have declined in this region, with potential additional negative impacts to breeding success. I used information from aerial surveys conducted between 2006 and 2017 in Khwai and Linyanti, two of the most important breeding areas for this species in northern Botswana to examine changes in nesting numbers and breeding success. The results showed a 53.5% decline in nesting numbers from these colonies, from 99 pairs in 2007 to 46 in 2017; with a greater decline in Linyanti than in Khwai. In both areas breeding success was significantly lower in 2017 than it was ten years ago. Current breeding success rates were generally lower than for other populations in South Africa. A population viability analysis suggested that if the productivity levels detected in 2017 were a true indication of current levels of productivity for this population, and if recent poisoning rates continue, this population has a high probability of extinction in the next 5 to 13 years.
139

Large vegetated termitaria and fire impacts on reptilitan community assemblage in a miombo woodland system heavily impacted by elephants

Heermans, Ben Cooper January 2010 (has links)
No description available.
140

Mapping the sensitivity of Lesotho's avifauna to wind farm developments

Sands, Dara January 2015 (has links)
Anthropogenically induced climate change, coupled with the volatility of world oil markets, has accelerated the global implementation of a variety of renewable energy technologies (RETs). The southern African nation of Lesotho aims to utilise its aeolian resources by harnessing the power of the wind through the development of wind farms. The Lesotho government has approved the development of a 42 turbine wind farm in the Maluti-Drakensberg in north-eastern Lesotho. The development of a wind farm in this area is predicted to result in significant negative impacts on globally important populations of Bearded Vulture Gypaetus barbatus and Cape Vulture Gyps coprotheres, in addition to six other red-listed species, including Black Stork Ciconia nigra and Southern Bald Ibis Geronticus calvus. Concern over the impacts of wind farms on Lesotho's avifauna has resulted in calls for the development of an avian sensitivity map. Sensitivity maps have been developed in many countries, including South Africa, in order to provide locational guidance for the siting of wind farms and indicate areas where the development of wind farms could potentially result in negative impacts on sensitive bird species. This study has developed an avian sensitivity map for Lesotho by creating a species sensitivity index to determine the potential sensitivity of Lesotho's avifauna to wind farms and then mapping the distributions of 14 bird species considered most at risk to identify areas of "medium", "high", "very high", "maximum" and"unknown" senstivity. Individual species maps were converted to 1-km square resolution allowing for a Composite scoring map, selecting the highest sensitivity score for each square, and a Cumulative scoring map, summing all sensitivity score within each square, to be created.

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