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Towards a better grasp of what matters in view of ‘the posts’

- O'Donoghue, Rob B, Lotz-Sisitka, Heila

  • Authors: O'Donoghue, Rob B , Lotz-Sisitka, Heila
  • Date: 2005
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/182693 , vital:43854 , xlink:href="https://doi.org/10.1080/13504620500169593"
  • Description: This response to McKenzie suggests that the issues of representivity, legitimacy and politics, inscribed within an institutional continuism characteristic of modernity within the McKenzie discourse, could well be recast within a reflexive view informed by insights derived with developing social theory. It briefly overviews the struggle for human agency that played out within the deconstructive engagements of the posts and probes how perspectives in social theory are opening the way for a break with features of environmental education as an institutional field. The review points to a reconstituting of the idea of environmental education research from scholastic field of/for environmental awareness and sustainable development, to a reflexive engagement within processes of social reproduction and reorientation in a changing world. A shift such as this would constitute a subtle change in a developing field of research, to situated design decisions of reflexive engagement (research) in social fields constituted within developing cultural contexts of risk.
  • Full Text:
  • Date Issued: 2005

Towards a Classification of Intrusion Strength

- Motara, Yusuf M, Irwin, Barry V W

  • Authors: Motara, Yusuf M , Irwin, Barry V W
  • Date: 2005
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/428261 , vital:72498 , https://www.researchgate.net/profile/Yusuf-Mota-ra/publication/267206150_Towards_a_Classification_of_Intru-sion_Strength/links/547485820cf245eb436de34e/Towards-a-Classification-of-Intrusion-Strength.pdf
  • Description: This paper proposes a new term, “intrusion strength”, for use by the se-curity community and those affected by compromised systems. It justi-fies the usefulness of such a term, proposes a preliminary ranking of intrusion strength factors, and concludes by mentioning the work nec-essary to create a full taxonomy of intrusion strength.
  • Full Text:
  • Date Issued: 2005

Towards an economic valuation of biodiversity: freshwater ecosystems

- Antrobus, Geoffrey G, Law, Matt

  • Authors: Antrobus, Geoffrey G , Law, Matt
  • Date: 2005
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/143013 , vital:38185 , http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.620.4217andrep=rep1andtype=pdf
  • Description: The valuation of environmental resources and biodiversity as a whole has become an increasingly necessary topic of research as our understanding of the importance and benefits of the healthy functioning of the environment develops. A major shortcoming of current research is that there has been very little advance in the valuation of freshwater biodiversity. The paper examines the socioeconomic importance of biodiversity and outlines the fundamentals of economic valuation thereof. The difficulties associated with the valuation of freshwater ecosystems are outlined and the results of a study presented to the South African Water Research Commission incorporating resource economics into freshwater quality objectives is described. The valuation of freshwater biodiversity is an important and complicated task that needs close attention in future research.
  • Full Text:
  • Date Issued: 2005

Towards an Infrastructural Framework for Secure Electronic Publication

- Forrester, Jock, Irwin, Barry V W

  • Authors: Forrester, Jock , Irwin, Barry V W
  • Date: 2005
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/428274 , vital:72499 , https://d1wqtxts1xzle7.cloudfront.net/3456213/No_147_-_Forrester-libre.pdf?1390832679=andresponse-content-disposi-tion=inline%3B+filename%3DTowards_an_Infrastructural_Framework_for.pdfandExpires=1714791785andSignature=TY2i5fIQcyv493crTdmDaMEDLBmnqe-s1yjeJ4OAk~-Syb12yZ1EBj-cJi8jxrmIorji6THEB4kSon43fOBcA5XUwoZ0H1T~LooHIyiqhBymL2ZtszKbFdqu1zZCrCkfR1YYAjUiVaM2BNSyC-P-mtY6S5aFcwztHl43eogmS70AIt0x76p9gIvL3xQsyE-VXBrtOrbkbQweUmgZs80bQDMnS-oou481C0BJyp8y6St6BETLKCaJC~uPYzrHOG1CwVxNZQoz38zJ3pLIzuNmdLcrlts3BbASji3c53MY-CoEGflXljrvzG6f85EBo-Oy9kjyAzvJ9gZmfISayfA-~w__andKey-Pair-Id=APKAJLOHF5GGSLRBV4ZA
  • Description: To prevent the accidental, or deliberate, publication of documents contain-ing hidden information the organisation needs to have an Electronic Publi-cation Policy, more importantly though, it needs to have the Technical Infra-structure in place to enforce the policy. This paper outlines such a Technical Infrastructure.
  • Full Text:
  • Date Issued: 2005

Towards the development of a protocol for rearing juvenile rock lobster, Jasus lalandii

- Esterhuizen, J. A

  • Authors: Esterhuizen, J. A
  • Date: 2005
  • Subjects: Lobsters -- Growth , Lobster fisheries -- South Africa , Crustacea -- Growth , Crustacea -- South Africa , Jasus lalandii , Lobster culture
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5328 , http://hdl.handle.net/10962/d1005174 , Lobsters -- Growth , Lobster fisheries -- South Africa , Crustacea -- Growth , Crustacea -- South Africa , Jasus lalandii , Lobster culture
  • Description: The diversification of current aquaculture practise in South Africa is crucial for the future development of the industry. The rock lobster, Jasus lalandii has been identified as a possible candidate species for shore based culture in systems similar to those used for abalone farming. Reduced Total Allowable Catch (TAC's) and an increased minimum legal size were implemented as management strategies to relieve fishing pressure on natural stocks of J. lalandii, and in turn led to increased market demand and a possible niche for farmed lobsters. High puerulus settlement along the Namibian coast, together with other favourable aquaculture attributes, indicate that the commercial grow out of wild harvested juveniles could be feasible. The aim of study was to investigate the feasibility of growing out rock lobsters in shore based systems in Namibia and South Africa. The experimental objectives of the project were to investigate the nutritional requirements, as well as the effect of stocking density and tank design on growth and survival of J. lalandii. The economic viability of shore based rock lobster farming was then evaluated based on the experimental results and typical capital requirements of an abalone farm in South Africa. Puerulus and early juvenile rock lobsters were collected in Luderitz, Namibia and transported to HIK Abalone Farm in Hermanus, South Africa where they were acclimated in black fibre glass tanks in a flow through system. The pueruli were stocked at 50, 75, 100 and 125/m² and early juveniles at 20, 30, 40 and 50/m² to test the effect of density on growth and survival. A comparative dietary study with both size classes was conducted using a mussel diet (Choromytilus meridionalis and Mytilus galloprovincialis), a commercial shrimp feed diet and a rotational diet comprising both mussels and shrimp feed. Tanks provided with "v-shaped" asbestos hides, PVC hides and no hides were compared to test the effect on growth rate and survival of pueruli. All treatments were conducted in triplicate. Temperatures were recorded twice daily while water quality parameters were tested every second week. The results indicate that density had a significant effect on growth and survival on post-pueruli. An initial stocking density of 75 post-pueruli/m² is regarded as optimal both in terms of the growth rate and biomass production per tank. No differences in growth and survival rates were attained in the early juvenile size class. This indicates that higher densities can be used to rear juvenile J. lalandii. No significant differences were obtained in growth rate when reared under different hide conditions although asbestos hides yielded significantly higher survival rates (93.3 %) compared to the tanks provided with PVC hides (74.04 %) and no hides (77.8 %, p≤0.05). As a result of the high survival rate observed in tanks provided with "V-shaped" asbestos hides, these tanks also yielded higher biomass production per tank (297.8 grams) compared to the tanks provided with PVC hides and no hides (261.09 and 260.5 grams respectively). In the diet trials, growth rates of post pueruli and juvenile lobsters fed the mussel and rotational (mussel and shrimp feed) diets did not differ significantly, however, growth rates of lobsters fed the shrimp feed only diet was significantly lower than both the mussel and rotational diets (p≤0.05). Lobsters fed the mussel diet yielded significantly higher survival rates compared to lobsters fed either the rotational diet or shrimp feed diet only. An imbalance in the fatty acid profile of the shrimp feed could have been a major contributing factor to the poor growth and survival in lobsters fed the shrimp feed only diet as the level of linoleic acid (LOA) was exceptionally high resulting in a high (n -6):(n-3) ratio (1.01) compared to the mussel and rotational diets (0.17 and 0.56 respectively). The low level of arachidonic acid (ARA) in the shrimp feed diet could be a further contributing factor explaning for the poor growth and survival of juvenile rock lobsters. An economic feasibility study was conducted at the end of the experimental phase by modelling a hypothetical shore based rock lobster farm. A projection of production costs and revenues was based on the typical costs of a shore based abalone farm and the current market prices for wild harvested J. lalandii. The economic viability was evaluated using benefit-cost ratios, payback period, internal rate of return and breakeven analysis. Sensitivity analyses revealed that the projected lobster growth and survival rates were the main biological factors influencing the economic feasibility of the hypothetical rock lobster farm. An assumed four year grow out period at a low stocking density yielded more lucrative internal rate of return (IRR), benefit-cost ratio, payback period and net present values (NPV) than a five year grow out period at a high density. The four year grow out scenario proved to be more robust to the fluctuating Rand/US$ exchange rate and could accommodate a lower lobster survival rate. Results presented in this study indicate that rock lobster farming is a marginal commercial prospect based on current production performance and costs. Further research to develop effective puerulus collection techniques as well as to make lobster grow out technology more cost effective is required.
  • Full Text:
  • Date Issued: 2005

Towards the development of a protocol for the selection of probiotics in marine fish larviculture

- Vine, Niall Gordon

  • Authors: Vine, Niall Gordon
  • Date: 2005
  • Subjects: Marine fishes -- Larvae Bacteria Fishes -- Microbiology Fish culture
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5329 , http://hdl.handle.net/10962/d1005175
  • Description: Manipulation or control of the microbiological aquaculture environment has been identified as an important focus area for future hatchery development. Subsequently, alternatives to obtain control of the microbiological environment are being sought of which the field of probiotics appears highly promising. Probiotics are usually selected based on various in vitro characteristics, however, the methods used differ and are sometimes unsuccessful due to poor experimentation. The aim of this work is to contribute towards the development of a protocol for the in vitro screening of bacterial candidate probiotics for marine fish larviculture. To reduce the number of candidate probiotics to be tested in vivo, various in vitro experiments need to be conducted, each screening for a particular mode of action – antagonism towards pathogen through production of antimicrobial compounds, growth and attachment to fish intestinal mucus, and the production of other beneficial compounds such as vitamins, fatty-acids and digestive enzymes. A total of 108 bacteria species were isolated from the digestive tract of the adult common clownfish, Amphiprion percula to screen for potential probiotics to be used in clownfish larval rearing. The antagonistic compounds assay identified twelve isolates which showed antagonism towards two or more aquatic pathogens. This was followed by an in vitro test that involved growing the organisms in fish intestinal mucus and modeling their growth parameters. A ranking index (RI) was developed using the lag period (λ) and doubling time (td) of the organism, where (1over λ x td) x 100. Five candidate probionts (AP1-AP5) with varied growth parameters were used for further in vitro experiments. The attachment to mucus assay introduced a novel tool for quantifying competition for attachment sites between candidate probionts and pathogens on mucus. Candidate probiont Pseudoalteromonas AP5 reduced the attachment ability of Vibrio alginolyticus when added before the pathogen and partially out-competed the pathogen for attachment sites when added second. In vitro screening for the production of beneficial compounds tested the candidate probiotics’ ability to produce digestive enzymes - trypsin, lipase and alkaline phosphatase as well as carotenoids and vitamin C. Candidate probiont Pseudoalteromonas AP5 produced high levels of the enzymes (98.2, 34.1 and 91.3 mU product liberated.ml⁻¹, respectively) and contained carotenoids while Kocuria AP4 contained carotenoids but produced low quantities of enzymes (7.8, 0 and 59 mU product liberated.ml⁻¹, respectively). None of the candidate probiotics produced vitamin C. To eliminate potential pathogenic or toxic candidate probionts, Artemia nauplii were exposed to each candidate probiont and the percentage Artemia mortality after 24-hours was determined. Candidate probiont AP2 caused high mortality of Artemia nauplii (98.4%) and was excluded from further studies. Identification of candidate probionts AP3-AP5 was performed using 16S-rDNA molecular techniques and the bacteria were assigned the names Bacillus AP3, Kocuria AP4 and Pseudoalteromonas AP5, respectively. Two methods of larval probiont delivery were tested – attachment to Artemia, and in-water delivery. Attachment to Artemia was high for both Kocuria AP4 and Pseudoalteromonas AP5 (7.2 x10³ and 2.7x10⁴ bacteria.nauplius⁻¹, respectively) while the in-water viability experiment showed that Kocuria AP4 comprised 23.9% of the total culturable water microflora after 24 hours while Pseudoalteromonas AP5 contributed 100%. To validate the findings from the in vitro experiments, in vivo trials using clownfish larvae were performed. Of the four candidate probiotics tested, only Kocuria AP4 showed potential to increase larval survival. In vitro tests produced a better understanding of the possible mode of action and strategies of competition between bacteria, however, the number of criteria in which a candidate probiont is successful in vitro may not be the best predictor for its effectiveness in vivo. Commercial studies that reduce between-treatment variation are required to test predictions about the most suitable probiont or combinations thereof.
  • Full Text:
  • Date Issued: 2005

Training needs for municipal employees: a case study of Makana Municipality

- Hamaamba, Tyson

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