• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 105
  • 27
  • 16
  • 15
  • 10
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 213
  • 41
  • 29
  • 29
  • 25
  • 22
  • 20
  • 17
  • 16
  • 16
  • 16
  • 15
  • 15
  • 14
  • 13
  • 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

Where did we go wrong? : a critical assessment of management in the Bluff Oyster Fishery

Knight, Peter David, n/a January 2008 (has links)
More than a century of dredging for oysters in the Foveaux Strait has resulted in a decimated fishery. In 1999 the Parliamentary Commissioner for the Environment asked the question: Where did we go wrong? This thesis provides answers to this question by presenting information provided by the Bluff oyster fishermen. In order to gain as much exposure to the community of fishermen as possible, a cumulative period of approximately six months was spent living in the town of Bluff between 2002 and 2007. During this time relationships were built with key informants, and a total of more than 50 community members were interviewed. The thesis describes the practical knowledge of the oyster fishermen, and places it in the context of more that 40 years of modem scientific studies concerned with the fishery. The finding are that since 1996 when the Quota Management System was introduced in the fishery, the most knowledgeable and responsible people in the fishery have been systematically excluded from roles in management. The practical knowledge of fishermen has been discounted in an industry and government led management system, which is an elaborate justification for continued maximum exploitation of the fishery. The theoretical contribution of the thesis lies in its description of belonging as a factor as important as that of property-rights in a sustainable resource system. The practical knowledge and conservation-mindedness of the fishery elders are characteristics of belonging, but not necessarily of ownership. Fishery management should recognize belonging as cultural capital, and make use of it under the present system (i.e. the Quota Management System) by according fishermen rights of management and access to the oyster fishery.
132

Low-temperature post-harvest processing for reducing Vibrio parahaemolyticus and Vibrio vulnificus in raw oysters

Chae, Minjung 29 June 2007 (has links)
Oysters are filter-feeding bivalves, which filter water for nutrients and often accumulate contaminants and human pathogens such as Vibrio parahaemolyticus and Vibrio vulnificus naturally occurring in the marine environment. These naturally occurring pathogens have been frequently isolated from raw shellfish, particularly oyster, in the United States and are recognized as the leading causes of human gastroenteritis associated with seafood consumption. Human illness caused by consumption of raw oyster contaminated with V. parahaemolyticus and Vibrio vulnificus typically results in reduced sales of oysters and a consequent significant financial burden for the producers. The United States produces more than 27 million pounds of oysters each year with a large portion of them being produced from the coastal water of the Gulf of Mexico. It is estimated that 20 million Americans eat raw shellfish and consumption of raw oyster is responsible for about 95% of all deaths associated with seafood consumption in the U.S., making raw oysters one of the most hazardous seafoods. Several post-harvest processes, including low temperature pasteurization, freezing, high pressure processing and irradiation, have been reported capable of reducing Vibrio contamination in raw oysters. However, most of them require either a significant amount of initial investment or operation costs, and oysters are often killed during processing. Cost-effective post-harvest processing for reducing V. parahaemolyticus in raw oysters without significant adverse effects on the oysters remains to be developed. This study was conducted to determine impacts of low-temperature (15, 10 and 5°C) depuration and frozen storage on reducing V. parahaemolyticus and V. vulnificus in raw oysters. Depuration of the Gulf oyster (Crassostrea virginica) with electrolyzed oxidizing (EO) water (chlorine, 30 ppm; pH 2.82; oxidation-reduction potential, 1,131mV) containing 3% NaCl was found ineffective on reducing both V. parahaemolyticus and V. vulnificus in the oysters. Reductions of V. parahaemolyticus and V. vulnificus in oyster after 48 h of EO water depuration at 22°C were limited to 0.7 and 1.4 log MPN/g, respectively. Depuration with EO water at lower temperatures did not enhance reductions of Vibrio in the oysters. Greater reductions of V. parahaemolyticus (1.2 log MPN/g) and V. vulnificus (2.0 log MPN/g) were observed when the oysters were depurated with artificial seawater (ASW) at room temperature (22°C) for 48 h. Decreasing temperature of ASW to 15°C for depuration significantly increased the reductions of V. parahaemolyticus and V. vulnificus to 2.1 and 2.9 log MPN/g, respectively, after 48 h of process. However, depuration of oyster in ASW at 10 and 5°C were found less effective than at 15°C in reducing Vibrio in the Gulf oysters. An extended depuration with ASW at 15°C for 96 h was capable of achieving 2.6 and 3.3 log MPN/g of reductions of V. parahaemolyticus and V. vulnificus, respectively, in the Gulf oysters. Study of effects of frozen storage at -10, -23 and -30°C on reducing V. parahaemolyticus in raw half-shell Pacific oyster (Crassostrea gigas) found that the population of the bacterium decreased faster in oysters stored at -10 than at -23 or -30°C. Holding half-shell Pacific oyster at -10°C for three months or at -23°C for four months was capable of achieving a greater than 3-log (MPN/g) reduction of V. parahaemolyticus in the Pacific oyster. / Graduation date: 2008
133

Poverty alleviation and biodiversity conservation in rural Brazil: a case study of the Cananeia Oyster Producers' Cooperative

Medeiros, Dean 28 March 2006 (has links)
The designation and enforcement of protected areas in southeast Brazil severely restricted livelihoods of rural inhabitants, who had limited options to adapt to new settings. Serious challenges emerged from deficiency in local capacity for the organization, management, and application of mitigation interventions. However, the Cananéia Oyster Producers’ Cooperative managed to overcome numerous challenges and was a finalist for the United Nations Development Programme’s 2002 Equator Prize for simultaneous poverty alleviation and biodiversity conservation. Qualitative research methods, including Rapid Rural Appraisal tools, were employed to examine the cooperative’s self-organization, cross-scale institutional linkages, and livelihood and conservation impact. Through various coordinated endevours such as the adoption of oyster rearing beds, depuration station, education, and designation of an extractive reserve, cooperative members have been able to improve their livelihoods while minimizing environmental impact. Lessons learned from the cooperative on simultaneous poverty alleviation and biodiversity conservation are presented in the final chapter of this thesis. / May 2006
134

Poverty alleviation and biodiversity conservation in rural Brazil: a case study of the Cananeia Oyster Producers' Cooperative

Medeiros, Dean 28 March 2006 (has links)
The designation and enforcement of protected areas in southeast Brazil severely restricted livelihoods of rural inhabitants, who had limited options to adapt to new settings. Serious challenges emerged from deficiency in local capacity for the organization, management, and application of mitigation interventions. However, the Cananéia Oyster Producers’ Cooperative managed to overcome numerous challenges and was a finalist for the United Nations Development Programme’s 2002 Equator Prize for simultaneous poverty alleviation and biodiversity conservation. Qualitative research methods, including Rapid Rural Appraisal tools, were employed to examine the cooperative’s self-organization, cross-scale institutional linkages, and livelihood and conservation impact. Through various coordinated endevours such as the adoption of oyster rearing beds, depuration station, education, and designation of an extractive reserve, cooperative members have been able to improve their livelihoods while minimizing environmental impact. Lessons learned from the cooperative on simultaneous poverty alleviation and biodiversity conservation are presented in the final chapter of this thesis.
135

Poverty alleviation and biodiversity conservation in rural Brazil: a case study of the Cananeia Oyster Producers' Cooperative

Medeiros, Dean 28 March 2006 (has links)
The designation and enforcement of protected areas in southeast Brazil severely restricted livelihoods of rural inhabitants, who had limited options to adapt to new settings. Serious challenges emerged from deficiency in local capacity for the organization, management, and application of mitigation interventions. However, the Cananéia Oyster Producers’ Cooperative managed to overcome numerous challenges and was a finalist for the United Nations Development Programme’s 2002 Equator Prize for simultaneous poverty alleviation and biodiversity conservation. Qualitative research methods, including Rapid Rural Appraisal tools, were employed to examine the cooperative’s self-organization, cross-scale institutional linkages, and livelihood and conservation impact. Through various coordinated endevours such as the adoption of oyster rearing beds, depuration station, education, and designation of an extractive reserve, cooperative members have been able to improve their livelihoods while minimizing environmental impact. Lessons learned from the cooperative on simultaneous poverty alleviation and biodiversity conservation are presented in the final chapter of this thesis.
136

Investigation of molecular mechanisms regulating biomineralization of pearl oyster Pinctada maxima

Gardner, Luke David January 2008 (has links)
Biomineralization is a process encompassing all mineral containing tissues produced within an organism. The most dynamic example of this process is the formation of the mollusk shell, comprising a variety of crystal phases and microstructures. The organic component incorporated within the shell is said to dictate this remarkable architecture. Subsequently, for the past decade considerable research have been undertaken to identify and characterize the protein components involved in biomineralization. Despite these efforts the general understanding of the process remains ambiguous. This study employs a novel molecular approach to further the elucidation of the shell biomineralization. A microarray platform has been custom generated (PmaxArray 1.0) from the pearl oyster Pinctada maxima. PmaxArray 1.0 consists of 4992 expressed sequence tags (ESTs) originating from the mantle, an organ involved in shell formation. This microarray has been used as the primary tool for three separate investigations in an effort to associate transcriptional gene expression from P. maxima to the process of shell biomineralization. The first investigation analyzes the spatial expression of ESTs throughout the mantle organ. The mantle was dissected into five discrete regions and each analyzed for gene expression with PmaxArray 1.0. Over 2000 ESTs were differentially expressed among the tissue sections, identifying five major expression regions. Three of these regions have been proposed to have shell formation functions belonging to nacre, prismatic calcite and periostracum. The spatial gene expression map was confirmed by in situ hybridization, localizing a subset of ESTs from each expression region to the same mantle area. Comparative sequence analysis of ESTs expressed in the proposed shell formation regions with the BLAST tool, revealed a number of the transcripts were novel while others showed significant sequence similarities to previously characterized shell formation genes. The second investigation correlates temporal EST expression during P. maxima larval ontogeny with transitions in shell mineralization during the same period. A timeline documenting the morphologicat microstructural and mineralogical shell characteristics of P. maxima throughout larval ontogeny has been established. Three different shell types were noted based on the physical characters and termed, prodissoconch I, prodissoconch 11 and dissoconch. PmaxArray 1.0 analyzed ESTs expression of animals throughout the larval development of P. maxima, noting up-regulation of 359 ESTs in association with the shell transitions from prodissoconch 1 to prodissoconch 11 to dissoconch. Comparative sequence analysis of these ESTs indicates a number of the transcripts are novel as well as showing significant sequence similarities between ESTs and known shell matrix associated genes and proteins. These ESTs are discussed in relation to the shell characters associated with their temporal expression. The third investigation uses PmaxArray 1.0 to analyze gene expression in the mantle tissue of P. maxima specimens exposed to sub-lethal concentrations of a shell-deforming toxin, tributyltin (TBT). The shell specific effects of TBT are used in this investigation to interpret differential expression of ESTs with respect to shell formation functions. A lethal and sublethal TBT concentration range was established for P. maxima, noting a concentration of 50 ng L- 1 TBT as sub-lethal over a 21 day period. Mantle tissue from P. maxima animals treated with 50 ng L- 1 TBT was assessed for differential EST expression with untreated control animals. A total of 102 ESTs were identified as differentially expressed in association with TBT exposure, comparative sequence identities included an up-regulation of immunity and detoxification related genes and down-regulation of several shell matrix genes. A number of transcripts encoding novel peptides were additionally identified. The potential actions of these genes are discussed with reference to TBT toxicity and shell biomineralization. This thesis has used a microarray platform to analyze gene expression in spatial, temporal and toxicity investigations, revealing the involvement of numerous gene transcripts in specific shell formation functions. Investigation of thousands of transcripts simultaneously has provided a holistic interpretation of the organic components regulating shell biomineralization.
137

Energy basis of a coastal region: Franklin County and Apalachicola Bay, Florida

Boynton, W. R. January 1975 (has links)
Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 376-388).
138

Influence of habitat complexity in structuring species-specific interactions and trophic linkages on oyster reefs of southeastern North Carolina /

Sonnier, Joseph M. January 2006 (has links) (PDF)
Thesis (M.S.)--University of North Carolina at Wilmington, 2006. / Includes bibliographical references (leaves: 53-59)
139

Poverty alleviation and biodiversity conservation in rural Brazil: a case study of the Cananeia Oyster Producers' Cooperative

Medeiros, Dean 28 March 2006 (has links)
The designation and enforcement of protected areas in southeast Brazil severely restricted livelihoods of rural inhabitants, who had limited options to adapt to new settings. Serious challenges emerged from deficiency in local capacity for the organization, management, and application of mitigation interventions. However, the Cananéia Oyster Producers’ Cooperative managed to overcome numerous challenges and was a finalist for the United Nations Development Programme’s 2002 Equator Prize for simultaneous poverty alleviation and biodiversity conservation. Qualitative research methods, including Rapid Rural Appraisal tools, were employed to examine the cooperative’s self-organization, cross-scale institutional linkages, and livelihood and conservation impact. Through various coordinated endevours such as the adoption of oyster rearing beds, depuration station, education, and designation of an extractive reserve, cooperative members have been able to improve their livelihoods while minimizing environmental impact. Lessons learned from the cooperative on simultaneous poverty alleviation and biodiversity conservation are presented in the final chapter of this thesis. / May 2006
140

The application of whole oyster shells in stormwater treatment removing heavy metals

Xu, Zhiying 24 August 2018 (has links)
Oyster shells are normally applied in wastewater treatment in the form of a powder; but the possibility of whole oyster shells removing metal ions in stormwater has not been investigated. The objectives of this research are to assess the application of whole oyster shells for removing metals in low concentration solutions and to explore the influence of the following factors: surface area of shells, initial concentration and exposure time, on removal efficiency. Experimental results demonstrated very good removal efficiency by oyster shells for removing copper, followed by cadmium and zinc; but was not effective in hexavalent chromium removal. Up to 70% removal can be reached in just one hour for copper with initial concentrations of 0.2ppm with 550cm2 of surface area (SA) of shells in a beaker experiment treating two-liter solutions (with an accompanying pH increase from 5 to 6.42). A removal efficiency (RE) of 57.7% and 33.3% was found for cadmium and zinc, respectively, with one day contact using shells of 300cm2 SA treating one liter of the lowest concentration solution; while only 14.3% was achieved for chromium under the same conditions. Mid-scale experiments with continuous inflow based on the 6-hour Saanich Design Storm demonstrated an 85.5% and an 83.9% RE of cadmium and copper in one day’s worth of contact time. There was no removal but in fact an increase in chromium and zinc was found for the mid-scale experiment. There was a positive relationship between initial concentration (IC) and removal efficiency for copper and zinc, but a negative relationship for chromium, while no relationship was found for cadmium. Up to 80% of copper can be removed at IC of 2.4ppm compared to 60% with IC of 0.65ppm with same amount of shells (by surface area). RE of 70%, 75% and 83% was observed for IC of 0.3ppm, 0.58ppm and 1.07ppm for zinc, respectively, with 154 cm2 SA. When IC of chromium is reduced from 1 ppm to 0.2ppm, RE tends to drop from 60% to 26%. There was also a positive relationship between SA and RE, and ET and RE. However, after a certain exposure time, increase in RE was negligible and sometimes, desorption would occur. Additionally, when the difference in surface area is small, the influence of this factor on RE was also small. When treating certain ranges of solution concentration, the effect of surface area on RE is difficult to distinguish. Moreover, the role of HRT in stormwater systems was not clearly found. / Graduate

Page generated in 0.2691 seconds