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Dissertations / Theses on the topic 'Oysters'

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Published: 4 June 2021
Last updated: 30 July 2024

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1

Harding, Juliana Maria. "Ecological interactions between benthic oyster reef fishes and oysters." W&M ScholarWorks, 2000. https://scholarworks.wm.edu/etd/1539616684.

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Restoration of oyster reef structures rehabilitates habitats and the multi-level ecological communities built on eastern oysters (Crassostrea virginica), the keystone species. Quantitative descriptions of ecological interactions within a habitat are required to delineate essential fish habitats for management and protection. Parallel development of primary (oysters) and secondary trophic levels (benthic fishes) offer an ecological metric of restoration progress over time. The interaction between larval oysters and larval fishes (e.g., Gobiosoma bosc, Chasmodes bosquianus) is quantitatively examined. Oyster settlement estimates for Palace Bar reef, Piankatank River, Virginia are of the same order of magnitude as field densities of recently settled oysters. Benthic fish settlement estimates are within an order of magnitude of observed adult densities. Zooplankton community composition around the reef is temporally variable and plankton densities range from 10 2--106 animals per m3 across temporal scales. Nocturnal densities of naked goby and striped blenny larvae around Palace Bar reef were 3 to 4 orders of magnitude higher than densities observed during daylight hours. Diurnal changes in larval fish abundance near Palace Bar reef are related to ambient light intensities and diurnal vertical migration by prey species. Naked goby, striped blenny, and feather blenny (Hypsoblennius hentzi) larvae selectively consumed bivalve veligers, in multi-factorial laboratory feeding experiments. Temporal co-occurrence of larval oysters and larval fishes was not observed in 1996 field collections although historic oyster settlement data strongly support the probability of co-occurrence during most years. Two different methods are used to estimate the larval oyster - larval fish interaction in the absence of field data. Given existing oyster and fish demographics on Palace Bar reef, larval fishes have the capacity to drastically reduce, perhaps eliminate, local veliger populations if they co-occur. The strength of this interaction is directly related to oyster demography-fecundity relationships. In the absence of veligers, larval fishes consume other plankton taxa that are abundant around the reef. Naked gobies and striped blennies are generalists. Oyster reefs provide optimal rather than essential habitat. Reef restoration will facilitate development of related ecological communities by providing optimal habitat conditions for these ubiquitous estuarine species.
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2

Fogelson, Susan B. "Effects of anoxia of histology, bacteriology, condition index, glycogen levels, and fecundity in the Eastern oyster Crassostrea virginica." Auburn, Ala, 2007. http://repo.lib.auburn.edu/2007%20Spring%20Theses/fogelson_susan_26.pdf.

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3

Colosimo, Sara L. "Comparison of Perkinsus marinus infection and oyster condition in southeastern North Carolina tidal creeks /." Electronic version (PDF), 2007. http://dl.uncw.edu/etd/2007-2/colosimos/saracolosimo.pdf.

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4

Chiu, May-chun Helen. "The ecology and energetics of Saccostrea cucullata (Born) : (Bivalvia : Ostreidae) in Hong Kong /." Hong Kong : University of Hong Kong, 1997. http://sunzi.lib.hku.hk/hkuto/record.jsp?B18597270.

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5

Perera, Percy. "Heavy metal concentrations in the Pacific oyster Crassostrea gigas thesis submitted in partial fulfilment of the degree of Master of Applied Science, Auckland University of Technology, September 2004." Full thesis. Abstract, 2004.

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6

Rubio, Ana M. "Environmental influences on the sustainable production of the Sydney rock oyster Saccostrea glomerata : a study in two Southeastern Australian estuaries /." View thesis entry in Australian Digital Theses Program, 2007. http://thesis.anu.edu.au/public/adt-ANU20080618.091057/index.html.

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7

Smeilus, Sarah E. "Effects of stock origin on the growth and survival of the eastern oyster, Crassostrea virginica, in southeastern North Carolina /." Electronic version (Miscrosoft Word), 2006. http://dl.uncw.edu/etd/2006/smeiluss/sarahsmeilus.doc.

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8

Carnegie, Ryan. "Distribution and Impact of the Oyster Parasite Bonamia Ostreae in Maine, and its Detection Using DNA Probes." Fogler Library, University of Maine, 2000. http://www.library.umaine.edu/theses/pdf/CarnegieRB2000.pdf.

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9

Zwerschke, Nadescha. "Ecological impacts of the spread of non-native oysters and interactions with native oysters." Thesis, Queen's University Belfast, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709886.

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Non-native species can have negative effects on local ecosystems by interrupting ecosystem functioning and altering biodiversity. Non-native ecosystem engineers, such as oysters, may have substantial impacts on ecosystems, by altering the physical structure of habitats and changing ecological processes within an invaded community. The non-native Pacific oyster, Crassostrea gigas, was introduced to Europe to revive the aquaculture industry, which was weakened following the decline of the native European flat oyster, Ostrea edulis. The introduction of C. gigas and subsequent natural proliferation in many coastal regions of Europe has caused great controversy in the scientific community. Initially, it was argued that C. gigas would have detrimental effects on the recovery of 0. edulis beds and alter the functioning of invaded coastal ecosystems. It has also been argued, however, that the spread of C. gigas often increased local biodiversity and reduced the impacts of coastal erosion. To assess the impact of C. gigas explicitly based on robust empirical evidence, an extensive survey and three field-based experiments were carried out. The aims were to: (i) identify and describe the current distribution of G. gigas populations in Ireland; (ii) test for direct effects of C. gigas on native 0. edulis beds; and (iii) characterise the functional ecology of C. gigas and compare it with the morphologically similar native species, 0. edulis.
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10

Artabane, Stephen J. "The effects of proximity to a subtidal channel on habitat utilization of intertidal oyster reefs /." Electronic version (PDF), 2006. http://dl.uncw.edu/etd/2006/artabanes/stephenartabane.pdf.

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11

Morrison, Christopher Michael. "Survival of Salmonella Newport in Oysters." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/194128.

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Salmonella enterica is a foodborne pathogen of major significance, and as such it has been extensively studied by researchers around the world. However, despite the numerous scientific publications on Salmonella, there are still many gaps in our understanding of its biology. One such gap is in the bacteria's interactions with invertebrate hosts, and in particular, oysters. Nearly 70 million pounds of oysters are consumed in the United States each year, and previous work in the Joens' laboratory found Salmonella in roughly 7% of the market oysters they sampled, with the majority of the isolates being the Newport serovar. The majority of oysters are consumed raw, which makes the presence of Salmonella within oysters a potentially significant food safety problem.To more closely examine the interactions between Salmonella and oysters, the Present Study developed a method to consistently and reproducibly raise oysters in a controlled laboratory environment in order to systematically expose them to enteric bacteria and quantify the amount of surviving bacteria at various time points after the initial exposure. Use of this model system throughout the Present Study led to four main conclusions.The first is that Salmonella enterica serovar Newport is capable of surviving in oysters for at least 60 days, from an average concentration of 3.7x103 CFU/g of oyster meat after 10 days, to over 102 CFU/g of oyster meat after 60 days. The second main conclusion is that the Newport serovar of Salmonella, which was found in such predominance in the earlier Joens' laboratory study, does not appear to have any special adaptations for survival within oysters, as other strains of Newport and other serovars of Salmonella survived equally well within our model. The third main conclusion, based on the results of immunohistochemistry, is that the relationship between Salmonella and oysters is not a transient interaction that is limited to the outside of the oyster's gut epithelium, but involves a long-term colonization inside the oysters' connective tissues. Because the survival of Salmonella in oysters could be of a pathogenic nature, the Present Study knocked out two key type III secretion systems (T3SS) found in two distinct Salmonella pathogenicity islands (SPI-1 and SPI-2) known to be critical for pathogenesis in mammalian hosts and examined their role in the bacteria's ability to survive within oysters. The results revealed that neither the SPI-1 nor the SPI-2 T3SS were necessary for Salmonella's survival in oysters, which led to the final conclusion of the Present Study that the nature of Salmonella's infection of oysters is fundamentally different than the pathogenesis that occurs in mammalian hosts and that further study of the mechanisms of the survival of Salmonella in oysters is needed to better understand the important and interesting relationship between a significant source of food and this common, and occasionally deadly, foodborne pathogen.
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12

Bearham, Douglas. "Identification and characterisation of two haplosporidian parasites of oysters in north Western Australia." Thesis, Bearham, Douglas (2008) Identification and characterisation of two haplosporidian parasites of oysters in north Western Australia. PhD thesis, Murdoch University, 2008. https://researchrepository.murdoch.edu.au/id/eprint/444/.

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A cryptic haplosporidian parasite was detected infecting rock oysters from the Montebello Islands in north-western Australia using a PCR targeting the parasite's small ribosomal subunit gene. The PCR products were cloned and sequenced along with the remaining sections of the parasite's SSU rRNA gene. Phylogenetic analysis of the sequence generated indicated a Minchinia species (Haplosporidia). The SSU sequence generated was used to develop two in situ hybridisation assays to visualise the parasite in H/E sections as well as a PCR assay to detect the parasite. The molecular assays were assessed for specificity and sensitivity and were then used to compare the parasite to previous haplosporidian parasite infections of pearl oysters. Both assays produced positive results from the infected pearl oysters but not from other closely related haplosporidian species. An SEM and TEM electron microscopy analysis was performed on spores from both parasite species. The spores of the pearl oyster parasite had two spore wall filaments wound around the spore originating for a posterior thickening while the spores of the rock oyster parasite were covered in microtubule-like structures. These data suggests pearl oysters where co-infected with both the Haplosporidium sp. and the Minchinia sp. detected in rock oysters. No evidence of a posterior thickening could be found on the spores of the rock oyster parasite. Attempts to detect the parasite at the previous geographic sites of its detection in pearl oysters resulted in detection of the Minchinia species in tropical oysters in the Kimberley region of Western Australia by in-situ hybridisation.
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13

Bearham, Douglas. "Identification and characterisation of two haplosporidian parasites of oysters in north Western Australia." Bearham, Douglas (2008) Identification and characterisation of two haplosporidian parasites of oysters in north Western Australia. PhD thesis, Murdoch University, 2008. http://researchrepository.murdoch.edu.au/444/.

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A cryptic haplosporidian parasite was detected infecting rock oysters from the Montebello Islands in north-western Australia using a PCR targeting the parasite's small ribosomal subunit gene. The PCR products were cloned and sequenced along with the remaining sections of the parasite's SSU rRNA gene. Phylogenetic analysis of the sequence generated indicated a Minchinia species (Haplosporidia). The SSU sequence generated was used to develop two in situ hybridisation assays to visualise the parasite in H/E sections as well as a PCR assay to detect the parasite. The molecular assays were assessed for specificity and sensitivity and were then used to compare the parasite to previous haplosporidian parasite infections of pearl oysters. Both assays produced positive results from the infected pearl oysters but not from other closely related haplosporidian species. An SEM and TEM electron microscopy analysis was performed on spores from both parasite species. The spores of the pearl oyster parasite had two spore wall filaments wound around the spore originating for a posterior thickening while the spores of the rock oyster parasite were covered in microtubule-like structures. These data suggests pearl oysters where co-infected with both the Haplosporidium sp. and the Minchinia sp. detected in rock oysters. No evidence of a posterior thickening could be found on the spores of the rock oyster parasite. Attempts to detect the parasite at the previous geographic sites of its detection in pearl oysters resulted in detection of the Minchinia species in tropical oysters in the Kimberley region of Western Australia by in-situ hybridisation.
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14

Bienlien, Lydia M. "Influence of Perkinsus Marinus Infection and Oyster Health on Levels of Human-Pathogenic Vibrios in Oysters." W&M ScholarWorks, 2016. https://scholarworks.wm.edu/etd/1477068161.

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The eastern oyster Crassostrea virginica is an ecologically and commercially important species whose natural populations have been devastated by overharvesting, habitat destruction, and disease, but the rapid growth of oyster aquaculture has shown potential to restore the economic significance of this species. A key threat to the growth and sustainability of oyster aquaculture is the association of human-pathogenic Vibrio bacteria with product marketed for raw consumption. Two Vibrio species, Vibrio vulnificus and Vibrio parahaemolyticus, are the causes of the highest rates of seafood consumption-related mortality and gastrointestinal illness, respectively. Identification of the factors influencing V. vulnificus and V. parahaemolyticus prevalence and intensity in oysters is fundamental to better risk management. Within the oyster, these bacterial species interact with the same tissues as the prevalent oyster parasite, Perkinsus marinus, yet little is known about the effect of P. marinus infection on bacterial levels. Answering the fundamental question of whether P. marinus correlates with V. vulnificus and V. parahaemolyticus levels in oysters was the focus of this research. Oysters were deployed in the York River, Gloucester Point, VA, where both Vibrio species and P. marinus are endemic, and were sampled at five time points when levels of both P. marinus and Vibrio spp. were expected to be high in oysters. Abundance of all three organisms and pathogenic strains of V. parahaemolyticus were determined in individual oysters using molecular methods to investigate potential correlations between parasite and bacterial abundance. Additionally, the levels of V. vulnificus and V. parahaemolyticus in relation to histopathology associated with P. marinus infection and other conditions were determined. The following year, manipulation of P. marinus disease progression, which is slowed by lower salinities and favored by higher salinities, was attempted by deploying oysters at two additional sites of different salinities to gain insight into whether the timing of P. marinus infection emergence directly influences Vibrio levels. No correlation was observed between total abundance of P. marinus and either V. vulnificus or V. parahaemolyticus. Manipulation of P. marinus disease progression produced no effect on P. marinus emergence, so this yielded no insight into P. marinus-Vibrio interactions. Histopathological analyses did not reveal any correlations between P. marinus ranking, distribution, or associated tissue damage and Vibrio spp. levels. Though few in number, oysters infected by Haplosporidium nelsoni were characterized by higher levels of V. vulnificus, and oysters of peak gametogenic development had significantly higher levels of pathogenic strains of V. parahaemolyticus. The results with regard to H. nelsoni and gametogenic state warrant further study. The primary conclusion of this study is that oyster health has little influence on levels of human-pathogenic Vibrio species in oysters, inter-host variability in Vibrio levels is likely explained by other factors.
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15

Arumugaswamy, Ramakrishnaswamy, Hawkesbury Agricultural College, and Faculty of Food and Environmental Sciences. "Studies on the presence and survival of campylobacter species in the Sydney rock oyster (Crassostrea commercialia)." THESIS_FES_XXX_Arumugaswamy_R.xml, 1985. http://handle.uws.edu.au:8081/1959.7/412.

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A direct enrichment procedure has been developed for selectively recovering low numbers of Campylobacter jejuni and Campylobacter coli from oyster tissue. This procedure makes use of a selective enrichment step, using a broth medium composed of 2% proteose peptone, 1% yeast extract, 0.2% potassium L-aspartate, 0.25% sodium chloride as basal medium (PYA broth)plus 0.2% bacteriological charcoal, polymyxin (5000 IU/ litre), cefoperazone(30 mg/litre), trimethoprim (10 mg/litre), cycloheximide (50 mg/litre), sodium pyruvate (0.25g/litre), sodium metabisulphate (0.25g/litre) and ferrous sulphate (0.25g/litre). In this study the procedure has been used to study the occurrence of thermophilic campylobacters in Sydney rock oysters. Seventy nine samples were screened during the winter months of April to July in 1985. Approximately 8% of the samples contained C.jejuni and 6% of the samples were positive for C.coli. The survival of C.jejuni and C.coli in the Sydney rock oyster was also investigated and results discussed. In contaminated shell stock stored at 20 and 30 degrees Centigrade, C.jejuni and C.coli survived for periods varying from 2 to 9 days. The failure of the organism to multiply in oyster tissue at any of these temperatures studied is an important phenomenon.
Master of Science (Hons)
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16

Barnes, Brian B. "Interspecific Interactions in Oyster Reef Communities: The Effect of Established Fauna on Oyster Larval Recruitment." W&M ScholarWorks, 2008. http://www.vims.edu/library/Theses/Barnes08.pdf.

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17

Videt, Blaise. "Dynamique des paléoenvironnements à huîtres du Crétacé Supérieur nord-aquitain (SO France) et du Mio-Pliocène andalou (SE Espagne) : biodiversité, analyse séquentielle, biogéochimie /." Rennes, France : Géosciences-Rennes, Université de Rennes I, 2004. http://www.geosciences.univ-rennes1.fr/biblio/edition/MGR-Videt.htm.

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18

Martins, Ana Rita Dias. "Bioaccumlation and Infectivity of Norovirus in Oysters." Master's thesis, Faculdade de Farmácia da Universidade do Porto, 2009. http://hdl.handle.net/10216/63805.

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19

Martins, Ana Rita Dias. "Bioaccumlation and Infectivity of Norovirus in Oysters." Dissertação, Faculdade de Farmácia da Universidade do Porto, 2009. http://hdl.handle.net/10216/63805.

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20

Brooks, Jeremy David. "The aetiology of environmental stress responses and disease in bivalve molluscs." Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259996.

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21

Grason, Emily W. Miner Benjamin G. "Alien vs. predator : effects of a native predator on two invasive oyster drills and oysters in Washington State /." Online version, 2010. http://content.wwu.edu/cdm4/item_viewer.php?CISOROOT=/theses&CISOPTR=360&CISOBOX=1&REC=5.

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22

Boardman, Cynthia. "Host-Pathogen Interactions between Eastern Oysters (Crassostrea virginica) and the Bacterial Agent of Juvenile Oyster Disease (Roseovarius crassostreae)." Fogler Library, University of Maine, 2005. http://www.library.umaine.edu/theses/pdf/BoardmanC2005.pdf.

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23

Cox, Carrollyn. "Seasonal Changes in Fecundity of Oysters Crassostrea virginica (Gmelin): From Four Oyster Reefs in the James River, Virginia." W&M ScholarWorks, 1988. https://scholarworks.wm.edu/etd/1539617594.

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24

Harwell, Heather D. "Landscape aspects of oyster reefs : fragmentation and habitat utilization /." Electronic version (PDF), 2004. http://dl.uncw.edu/etd/2004/harwellh/heatherharwell.pdf.

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25

Sonnier, Joseph M. "Influence of habitat complexity in structuring species-specific interactions and trophic linkages on oyster reefs of southeastern North Carolina /." Electronic version (PDF), 2006. http://dl.uncw.edu/etd/2006/sonnierj/josephsonnier.pdf.

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26

Dew, Jodi Rebecca. "A population dynamic model assessing options for managing eastern oysters (Crassostrea virginica) and triploid Suminoe oysters (Crassostrea ariakensis) in Chesapeake Bay." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/33101.

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A demographic population simulation model was developed to examine alternative fishery management strategies and their likely effects on the probability of extirpation of local eastern oyster (Crassostrea virginica) populations in the Chesapeake Bay. Management strategies include varying the minimum shell length-at-harvest, harvest rate, and rate and frequency of stocking of oyster seed with respect to varying salinities and oyster population densities. We also examined the rate of disease-mediated mortality that can be tolerated by a viable population. High density populations at low salinity sites remained viable under a 100% harvest rate and 76.6 minimum shell length-at-harvest due to increased fertilization efficiency in high densities, which increased reproduction. Low density populations at low salinity sites remained viable when harvest rate was set at 0.5 and minimum shell length-at-harvest was set at 85 mm. Neither reducing harvest rate nor minimum shell length-at-harvest produced a viable population at high salinity sites. The effects of disease-mediated mortality were too great for these management options to decrease the probability of extirpation to zero. Supplemental stocking conducted regularly reduced extirpation probabilities to zero and pulse stocking (every five to ten years) did as well, although it required a much larger number of oysters to be stocked. Decreasing disease-mediated mortality rates by 20% in high density populations and by 80% in low density populations reduced the probability of extirpation to zero, suggesting the degree of genetic improvement needed to rebuild eastern oyster populations in the Chesapeake Bay. Culture of a non-native species, such as the Suminoe oyster (Crassostrea ariakensis), could supplement harvest of the declining eastern oyster fishery in Chesapeake Bay. Because of possible ecological impacts from introducing a fertile non-native species, introduction of sterile triploid oysters has been proposed. However, recent data show that a small percentage of triploid individuals progressively revert toward diploidy, introducing the possibility Suminoe oyster might establish self-sustaining populations. To assess the risk of Suminoe oyster populations becoming established in Chesapeake Bay, a demographic population model was developed. Inputs modeled included: salinity, stocking density, reversion rate, reproductive potential, natural and harvest mortality, growth rates, and effects of various management strategies, including harvest criteria. Results showed decreased probability of a Suminoe oyster population becoming self-sustaining when oysters are grown at low salinity sites, certainty of harvest is high, minimum shell length-at-harvest is small, and stocking density is low. Results of the model suggest management strategies that will decrease the probability of a Suminoe oyster population becoming self-sustaining. Policy makers and fishery managers can use the model to predict potential outcomes of policy decisions, supporting the ability to make science-based policy decisions about the proposed introduction of triploid Suminoe oysters into the Chesapeake Bay.
Master of Science
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27

Arumugaswamy, Ramakrishnaswamy. "Studies on the presence and survival of campylobacter species in the Sydney rock oyster (Crassostrea commercialia)." Thesis, View thesis, 1985. http://handle.uws.edu.au:8081/1959.7/412.

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A direct enrichment procedure has been developed for selectively recovering low numbers of Campylobacter jejuni and Campylobacter coli from oyster tissue. This procedure makes use of a selective enrichment step, using a broth medium composed of 2% proteose peptone, 1% yeast extract, 0.2% potassium L-aspartate, 0.25% sodium chloride as basal medium (PYA broth)plus 0.2% bacteriological charcoal, polymyxin (5000 IU/ litre), cefoperazone(30 mg/litre), trimethoprim (10 mg/litre), cycloheximide (50 mg/litre), sodium pyruvate (0.25g/litre), sodium metabisulphate (0.25g/litre) and ferrous sulphate (0.25g/litre). In this study the procedure has been used to study the occurrence of thermophilic campylobacters in Sydney rock oysters. Seventy nine samples were screened during the winter months of April to July in 1985. Approximately 8% of the samples contained C.jejuni and 6% of the samples were positive for C.coli. The survival of C.jejuni and C.coli in the Sydney rock oyster was also investigated and results discussed. In contaminated shell stock stored at 20 and 30 degrees Centigrade, C.jejuni and C.coli survived for periods varying from 2 to 9 days. The failure of the organism to multiply in oyster tissue at any of these temperatures studied is an important phenomenon.
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28

Dove, Michael Colin. "Effects of estuarine acidification on survival and growth of the Sydney rock oyster Saccostrea glomerata." Connect to this title online, 2003. http://www.library.unsw.edu.au/~thesis/adt-NUN/public/adt-NUN20050125.110005/index.html.

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29

Mitchell, Jennifer Diane Lockaby Bruce Graeme. "Biogeochemical Influence of Chinese privet in riparian forests in West Georgia and the Influence of oyster harvesting in Apalachicola Bay, Florida." Auburn, Ala, 2009. http://hdl.handle.net/10415/1717.

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30

Gibbs, Mitchell. "The impact of climate change on larvae of oysters." Thesis, The University of Sydney, 2020. https://hdl.handle.net/2123/24912.

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Marine larvae are a critical life history stage of marine molluscs which will be impacted by climate change. There is a pressing need to understand whether marine molluscs will have the capacity to adapt and persist in this era of rapid change. Transgenerational plasticity is a mechanism for rapid acclimation of marine organisms which result in resilient offspring when exposed to climate change. The overall aim of this thesis was to determine the impact of climate change on the larvae of the native Sydney rock oyster, Saccostrea glomerata and invasive Pacific oyster Magallana gigas. The main hypothesis tested was that whether responses of larvae would be improved through transgenerational exposure to climate change stress including warming and elevated pCO2CO2 on the morphological, physiological and lipid energetics. The experiments in this thesis showed that the larvae of M. gigas may be more robust than the larvae of S. glomerata when exposed to near future climate change conditions, however, S. glomerata may have a greater scope for transgenerational plasticity to cope with a changing climate. This thesis supports the idea that although transgenerational parental conditioning has been suggested as an acclimatory mechanism for marine organisms to cope with the stress of climate change it may not equally be a panacea to all conditions for all oyster species. This thesis has also demonstrated that larval mortality is not likely due to the expiration of lipid reserves when starved or exposed to warming and acidification. The findings of this thesis suggest that the dynamic between the native S. glomerata and invasive M. gigas may be altered as estuarine change in South eastern Australia accelerates. These findings will inform the global bivalve aquaculture industry worth $44 million to the state of New South Wales and $50 billion to the globe, which is at risk due to global climate change.
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31

Aguirre, Macedo Maria Leopoldina. "Study on helminth and other parasite communities of oysters." Thesis, University of Exeter, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337758.

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32

Chen, Luman. "Sensory and Chemical Characteristics of Eastern Oysters(Crassostrea virginica)." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/33860.

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Eastern Oysters, or Crassostrea virginica, are an important dietary component in the Chesapeake region and have supported a major fishery in the Chesapeake for more than 100 years. Virginia oysters do not always receive attention in up-scale markets. It is possible that the lack of information on sensory characteristics of Chesapeake oysters may contribute to this problem. In order to differentiate Chesapeake oysters from other oysters, a descriptive sensory test (n=8) was conducted and chemical composition attributes were measured, including glycogen content, proximate analysis, sodium chloride content, and fatty acid analysis. Statistical differences were found for the attributes: volume of liquor, gray/brown and tan colors, roundness of shell, plumpness and salty taste when comparing eastern oysters from Chesapeake to oysters from Rhode Island and New Brunswick, Canada. The glycogen contents in eastern oysters followed the reproductive cycle and glycogen increased from September to December, and started to decrease by April. There were small but significant (p<.05) differences in the contents of moisture, ash, protein and fat of oysters from Chesapeake and other areas. Oysters from Chesapeake had higher percentages of long-chain n-3 fatty acids, which were about 4 times higher than Beau Soleil, an oyster from New Brunswick, Canada. The high percentage of long chain n-3 fatty acids in Chesapeake oysters may be valuable for marketing.
Master of Science
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33

Brillhart, Crystal. "Prevalence and Genetics of Survival of Salmonella in Oysters." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/145280.

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Salmonella enterica is a leading cause of food-borne gastrointestinal disease worldwide. A survey conducted in 2002-2003 showed that oysters may contain Salmonella and thus may also be a source of salmonellosis. Since oysters are commonly consumed raw, no amount of food safety education will prevent consumers from ingesting a possibly infectious dose from Salmonella contaminated oysters. The research in this dissertation employed a combination of traditional culture techniques as well as genomics-based molecular applications to explore Salmonella infection in oysters and the subsequent risk to consumers of raw oysters. A year-long survey of oysters served on the half-shell in local restaurants determined that overall 1.2% of oysters were contaminated with Salmonella. Oysters containing Salmonella were found in 7 of the 8 months surveyed and 7 of the 8 restaurants served contaminated oysters. Six different serovars were isolated, but one strain of S. Newport, as determined by matching pulsed field gel electrophoresis patterns, represented 43% of the positive samples. Interestingly, this is the same strain that was predominantly isolated in the earlier survey of oysters and was also resistant to at least 7 different antimicrobials. The remainder of this dissertation work was an exploration of why this particular strain is seen so often in oyster infections. A custom microarray was used to perform a transposon site hybridization (TraSH) assay to identify genes that are necessary for S. Newport survival in the oyster. In this way, a negative selection was able to determine the genes that were necessary for S. Newport to survive in oysters. A subset of the genes identified by TraSH was selected and site-directed mutagenesis was performed to knock those genes out of LAJ160311. Oysters were infected with those mutant strains to test for their ability to survive in oysters and thereby determine the role of those individual genes in pathogenesis. The conclusions of the TraSH assay were that virulence factors that are essential for survival of Salmonella in mammalian models, particularly the type three secretion systems, may not be important in the oyster model. Motility provided by flagella was identified as a major virulence factor in oyster colonization by S. Newport.
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Denapolis, Tasia MV. "Legacy Habitat Suitability of eastern oysters (Crassostrea virginica) in Louisiana: a prelude to Mississippi River Delta freshwater diversions." ScholarWorks@UNO, 2018. https://scholarworks.uno.edu/td/2560.

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The Louisiana oyster industry is greatly impacted by freshwater and sediment diversions that are part of the effort to restore the state’s coastline. A habitat suitability index (HSI) proposes species-habitat relationships that can be instrumental in creating impact assessments and suitability predictions for management as new diversions are implemented. An oyster (Crassostrea virginica) HSI was developed using three variables crucial to oyster sustainability: average annual salinity, minimum monthly salinity, and average salinity during the spawning season. These Legacy HSI visualizations show annual fluctuations in the distribution of zones suitable for oyster cultivation prior to proposed diversions in Pontchartrain and Barataria Basins from 1967 to 2016. Modeling suitability based upon these variables can provide crucial information for timing the use of diversions to lessen harmful effects upon the oyster industry as well as indicate new potentially suitable areas that the diversions may create.
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Bucknavage, Martin M. "Growth and survival of Clostridium botulinum type E in pasturized oysters." Thesis, This resource online, 1988. http://scholar.lib.vt.edu/theses/available/etd-04122010-083636/.

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Lorca, Tatiana A. "An Evaluation of the Role of Temperature on the Safety and Quality of Raw Shellstock Oysters and Bluefish." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/35694.

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Raw oyster shellstock was subjected to abuse conditions (7, 13, and 21°C) and sampled over a ten day storage period to gather scientific data to aid in determining whether spoilage occurred in the raw product over time before proliferation of pathogenic flora (Vibrio vulnificus) made the product unsafe. Spoilage was evaluated through pH measurements of a homogenate of the shucked meat and liquor. The olfactory acceptability of the raw oysters was evaluated in concert with the microbial and chemical evaluations. At all storage conditions, halophilic bacteria outgrew V. vulnificus by a minimum of 1 log CFU/g oyster (Colony Forming Units per gram) (p < 0.05). Olfactory acceptability was below 40% when V. vulnificus growth was at its highest (p < 0.05). Refrigerated storage should be considered a CCP for raw shellstock since even moderate temperature control kept V. vulnificus below 104 approximately 1-2 Logs below the estimated infective dose for the majority of the population.
Master of Science
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McGinley, Susan. "Detecting Bacterial Pathogens in Oysters: Program Targets Campylobacter and Salmonella." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001. http://hdl.handle.net/10150/622254.

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38

Bento, Vânia Sofia de Oliveira. "Oysters return to the Tagus estuary through an ecological model." Master's thesis, FCT - UNL, 2008. http://hdl.handle.net/10362/1908.

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Dissertation submitted to the Faculty of Sciences and Technology of New University of Lisbon for obtaining the degree of Master in Environmental Management Systems
Aquaculture is an activity that has been increasing along the last years. Until the 1970’s Portugal and more specifically the Tagus estuary, was the major exporter of oysters in Europe. Factors like TBT and oysters gill disease had made that the shellfish aquaculture has never been again practised in Tagus estuary. According to that, this work intends to concept and to implement an ecological model that develops the oysters growth in order to them return to the estuary. To begin with, the model was calibrated with data from Database of 1980 and then validated with Database of 1982. The model results have shown a good correlation with measured data, so it was supposed as a good model. After that, it was simulated two different scenarios. The first one it was increased 30C in water temperature and in the second one it was changed the seeding day to the 90 day instead the 120 day. The results illustrate that in scenario I, the production of oysters decrease as well as the oyster individual weight and length, and in scenario II, however the oyster individual growth as decrease a little the oyster total harvest as increase. With these approaches, it will be possible to define the better conditions in order to achieve a good model that can be able to optimise the production of oyster in the Tagus estuary.
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39

Rodrigues, Das Chagas Pereira Roberta. "Responses of oysters to a changing climate in southeast Australia." Thesis, The University of Sydney, 2020. https://hdl.handle.net/2123/22424.

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Securing economically and ecologically significant oyster species, as our oceans warm and acidify from climate change, is a priority. Native oysters along the southeast coast of Australia will be particularly vulnerable to ocean change due the strengthening of the East Australian Current. Oysters form complex aggregations and reef structures which provide ecosystem services and habitat for several species in coastal and estuarine areas. The Sydney rock oyster Saccostrea glomerata and flat oyster Ostrea angasi are two native species with overlapping distribution in the state of New South Wales (NSW). Currently, both species are commercially cultivated and restoration projects are in progress in southern states. The overall aim of this thesis was to determine the impact of climate change stressors (warming and acidification) on these species to support their persistence and oyster reef restoration as anthropogenic actions modify our oceans. To detect effects of stressors in the capacity of energy gain through feeding, a laboratory experiment was done to evaluate responses of S. glomerata. Oysters responded to stressors by increasing standard metabolic rates (SMR), clearance, ingestion and absorption rates. Such responses suggest that climate change will alter feeding and metabolism of S. glomerata. To predict species responses to changing climate, experiments need to approximate conditions relevant to the region and species natural habitat. It was also investigated the impact of elevated temperature and pCO2 on O. angasi using outdoor flow through mesocosms in Sydney Harbour, NSW. Elevated temperature caused high mortality and decreased the condition of oysters. Elevated pCO2 increased SMR almost four-fold and lowered the extracellular pH. Based on these responses, Ostrea angasi will be living near the limits of its thermal tolerance as climate change worsen by 2050. The potential pathways oysters will use to cope and acclimate to climate change may “climate proof” aquaculture species and ensure reef restoration efforts. An experimental study was done where both species, O. angasi and S. glomerata, were given a mild dose of thermal stress in the laboratory (“stress inoculation”) and then transferred and exposed to warm seawater at Lake Macquarie, NSW for seven months. Shell growth, condition index, lipid content and survival of O. angasi and condition of S. glomerata were all significantly reduced by warming. Overall, in this thesis, S. glomerata were more resilient in their response to elevated pCO2 and temperature. Ostrea angasi had the greatest vulnerability to warming, which may be ameliorated by elevated pCO2. If we are to secure the great benefits oysters bring to coastal ecosystems, we need realistic experiments to predict their responses to climate change stressors. This thesis findings reinforce that project managers need to consider the current and future climate change in sustaining oyster reef restoration.
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Haupt, Tanya M. "History and status of oyster exploitation and culture in South Africa, and the role of oysters as vectors for marine alien species." Master's thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/8934.

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Includes bibliographical references (leaves 69-86).
In South Africa, both wild and cultivated oysters are consumed. Edible wild oysters include Striostrea margaritacea, Saccostrea cucullata, Ostrea atherstonei and 0. algoensis and all occur along the South and East coasts. These oysters were, or are, exploited commercially, recreationally and via subsistence fishers with S. margaritacea being the most targeted species. The commercial harvesting areas are along the Southern Cape coast and in KwaZulu-Natal. The Southern Cape coast is the largest harvesting area with 102 of the 145 pickers employed in the region. Commercial and recreational harvesting is managed by the Marine and Coastal Management Branch of the Department of Environmental Affairs and Tourism. Data on the total annual catch of oysters in these provinces are minimum estimates, as collectors do not always comply with the harvesting regulations. Subsistence harvesting is largely unmanaged, except in KZN, and is particularly rife in the Eastern Cape Province. The culture of oysters is dependent on importing Crassostrea gigas spat mostly from Chile. Oyster production statistics are only available since 1985, but approximately two million Crassostrea gigas oysters were produced annually throughout the seventies and early eighties. Since then, production has fluctuated over the years with an approximate increase of six million between 1985 and 1991, a decrease of five million between 1991 and 1998, and is presently stable. The establishment and closure of a highly productive farm in the late eighties and early nineties respectively, as well as improved production in recent years, has resulted in these trends. Although the market for oysters has grown, production has not kept up with demand, due to a lack of suitable locations for mariculture purposes. Finding suitable sites for oyster cultivation along the Northern Cape coast and establishing local oyster hatcheries for C. gigas oysters is suggested as the way forward. The latter would also prevent associated marine alien species from being imported with spat. Globally, oysters are well known vectors of marine alien species and despite oyster imports as early as 1894 into South Africa, this topic has been afforded little or no local attention. A visit to various oyster farms in South Africa resulted in the discovery of four newly-recorded alien species: the black sea urchin Tetrapygus niger, from Chile, the European flat oyster Ostrea edulis, thought to be locally extinct following its intentional introduction into South Africa in 1946, Montagu's crab Xantho incisus, from Europe, and the brachiopod Discinisca tenuis, from neighbouring Namibia. Oyster imports are suggested as their most likely vector into South Africa and the biological attributes of some emphasizes the possible threat and the need to limit or prevent their spread. Local or intraregional translocation of C. gigas and associated species, including aliens colonizing the area, may aid in this spread. Oysters host a diverse community of epi-and infaunal fouling taxa, which can be accidentally translocated along with their hosts in the course of commercial oyster trade. Thus, the types and quantities of fouling taxa occurring on farmed Crassostrea gigas were examined. How effectively these taxa are removed by standard cleansing techniques and whether those that persist after washing, survived intraregional translocation, were also examined. Cleaning and translocating oysters significantly reduced both the quantity (by more than 30 and 40 times respectively) and variety of fouling taxa. Although the mean abundance (A) or biomass (B) of taxa in uncleansed oysters (A: 79.48±233.10 (SD), B: 0.034±0.314 (SD)) were greatly reduced in cleansed oysters (A: 2.30±7.65 (SD), B: 0.0003±0.002 (SD)), small quantities still managed to survive translocation (A: 1.87± 7.43 (SD), B: 0.006±0.020 (SD)). Thus, the effectiveness of exposing oysters to freshwater or heated seawater as a more thorough cleansing regimen, to prevent the translocation of such taxa, were examined. Results indicated that oysters were able to survive for a longer time in freshwater (0% mortalities after 18 h) than in heated seawater (26.7% mortalities after 40 sec), but most taxa were eliminated more effectively by the latter treatment (e.g. 88.5% of the mudworm Polydora hoplura died after 20 sec compared to 97.5% after 18 h in freshwater). However, only a single reproductive individual of an alien species may be required for a successful introduction, and soaking for 20 sec in heated seawater would still be ineffective. An alternative treatment of 18 h in freshwater and 20 sec in heated seawater or freshwater, is suggested as a more effective treatment.
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41

Volety, Aswani K. "A study of the histozoic oyster parasite, Perkinsus marinus: I. Disease processes in American oysters (Crassostrea virginica). II. Biochemistry of Perkinsus marinus." W&M ScholarWorks, 1995. https://scholarworks.wm.edu/etd/1539616895.

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Numerous studies have investigated the disease processes of Perkinsus marinus in the oyster, Crassostrea virginica. However, the transmission dynamics and factors affecting P. marinus infection are still unclear. The objectives of this study were to investigate: (1) the principal and most effective lifestage of P. marinus, (2) the synergistic effects of temperature, salinity and P. marinus dose on disease prevalence, (3) suppression of host reactive oxygen intermediates by P. marinus, (4) the localization of acid phosphatase in the parasite, (5) the effects of temperature and salinity on acid phosphatase secretion, and (6) the P. marinus lipid and fatty acid composition. Meronts were more infective than prezoosporangia, and infectivity was dose dependent (100 cells minimum). High temperatures, salinities and P. marinus doses increased infection prevalence and intensity. Temperature was the most important factor influencing disease susceptibility, followed by cell dosage and salinity. Both temperature and salinity significantly affected the host cellular and humoral factors in oysters. P. marinus suppression of hemocyte reactive oxygen intermediates production, as assessed by chemiluminescence was dose dependent. Zymosan stimulated hemocyte chemiluminescence was reduced, suggesting that live P. marinus cells or their extra-cellular products suppress host reactive oxygen intermediates production. Acid phosphatase activity in P. marinus cells increased with increasing temperature. Meronts had higher acid phosphatase activity than prezoosporangia. Extracellular acid phosphatase secretion by P. marinus was dose dependent, increasing with temperature and osmolality. Electron microscopy revealed that acid phosphatase activity was localized primarily in the nucleus, but was also present in the cell membrane. Lipid classes of meronts resembled those found in their media. Phospholipids were the major lipid class in meronts, while triacylglycerols were dominant in prezoosporangia isolated from infected oyster tissue. Results indicated that meronts may be capable of interconversion of lipid classes. Both meronts and prezoosporangia had much higher levels of arachidonic acid than the host.
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42

Paranjpye, Rohinee. "The role of a Vibrio vulnificus type IV pilin in pathogenesis and in persistence in oysters /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/5372.

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43

Limthammahisorn, Suttinee Brady Yolanda Juanita Arias Covadonga R. "In vitro and in vivo cold shock response in Vibrio vulnificus." Auburn, Ala., 2007. http://repo.lib.auburn.edu/Send%2002-04-08/LIMTHAMMAHISORN_SUTTINEE_24.pdf.

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44

Chiu, May-chun Helen, and 趙美眞. "The ecology and energetics of Saccostrea cucullata (Born): (Bivalvia : Ostreidae) in Hong Kong." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1997. http://hub.hku.hk/bib/B31235669.

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45

Kural, Ayse G. "Temperature-assisted pressure inactivation of Vibrio parahaemolyticus and Vibrio vulnificus in oysters." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 89 p, 2007. http://proquest.umi.com/pqdweb?did=1338870531&sid=16&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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46

Lele, Vrushali. "Cumulative Risks to Eastern Oysters, Crassostrea virginica in the James River, VA." VCU Scholars Compass, 2011. http://scholarscompass.vcu.edu/etd/2472.

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In an effort to apply Cumulative Risk Assessment (CRA) as developed by the U.S. EPA, the present study investigates the cumulative risks to Eastern oysters due to multiple stressors such as salinity, temperature and oxygen and carbon dioxide. I also compared the effectiveness of the Hazard Quotient Method (HQ) in CRA. Ambient conditions in the James River, VA were obtained from the Virginia DEQ database and respiratory responses were estimated using values from the literature. The multiple environmental stresses are evaluated using a probabilistic analysis that combines the environmental conditions. It was concluded that salinity was the most influential stressor in the model. Other risks were identified contributing to the vulnerability of the oysters. Crystal Ball simulations yielded that the oxygen uptake of oysters reduced by more than 29%. The HQ method was found to be inappropriate in analyzing cumulative risks for CRA. Oyster populations are dramatically declining in the James River and the Chesapeake Bay. Hence, effective oyster restoration activities are underway to rebuild oyster populations in the James River and throughout the Bay area.
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Harsh, Deborah Armitage. "Filtration of Oysters in Patches: Effects of Water Flow and Seston Composition." W&M ScholarWorks, 1995. https://scholarworks.wm.edu/etd/1539617693.

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48

Li, Tong. "Lipid Class Composition of Oysters, Crassostrea virginica, Exposed to Sediment-Associated PAHs." W&M ScholarWorks, 1996. https://scholarworks.wm.edu/etd/1539617705.

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49

Haye, Jennifer Marcelle. "Role of natural organic matter in governing the bioavailability of toxic metals to american oysters." Texas A&M University, 2005. http://hdl.handle.net/1969.1/3796.

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Colloidal macromolecular organic matter (COM), which makes up a large portion of the bulk dissolved organic matter (DOM) in marine environments, has the capability to modify the bioavailability of potentially toxic metals to aquatic organisms. In order to better understand the bioavailability of some of these metals to estuarine bivalves, American Oysters (Crassostrea virginica) were exposed to different types of natural colloidal (COM) and model (alginic acid, carrageenan, and latex particles) organic biopolymers, tagged with gamma-emitting radioactive metal ions (110mAg, 109Cd, 57Co, 51Cr, 59Fe, 203Hg and 65Zn) or 14C (to sugar OH groups). Natural COM was obtained from Galveston Bay water by 0.5µm filtration, followed by cross-flow ultrafiltration, using a 1kDa ultrafilter, diafiltration and freeze-drying. COM and DOM model compounds were used in the bioavailability experiments at 2 ppm concentrations. Separate 16-hour experiments using varying sizes of latex particles assessed the lowest size of colloids that can be filtered from the water. Results showed that filter-feeding bivalves could efficiently remove particles as small as 0.04µm (40nm) in diameter, with removal halftimes of 2.5 to 5.5 hours, equivalent to filtration rates of about 50±15 ml/hour, or about 3 L d-1 g-1, which are typical values for these oysters. Results of the 20-hour bioavailability experiments demonstrated that oysters could effectively filter metals bound to COM, with the metals bound to alginic acid COM being removed at the highest rates from the water. However, the metals bound to alginic acid were not found in oyster meat in the highest amounts: it was the metals associated with the carrageenan COM. The 14C labeled biopolymer data also showed alginic acid to be removed from the water at the highest rate and, contrary to the metals, was also present in the meat in the greatest amounts. Thus, while previous experiments suggested that the quantity (i.e., concentration) of natural organic matter is important for metal bioavailability, it was shown here that the “quality”, i.e., the type of natural organic matter, is also a factor for controlling bioavailability, removal and incorporation rates of metals to oysters.
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Lee, Jung-Ho John. "The Role of Sediment Resuspension on Metal Uptake by Filter-Feeding Estuarine Organisms (Sydney Estuary, Australia)." Thesis, The University of Sydney, 2015. http://hdl.handle.net/2123/14306.

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Sediments in Sydney estuary are contaminated by metals including copper, lead and zinc and are resuspended into the water column due to natural and anthropogenic causes. These metals are also highly enriched in the tissues of the native filter-feeding oyster Saccostrea glomerata and is thought to be caused by the ingestion of resuspended sediments. To establish this link, a consolidated approach of field, laboratory and numerical analyses was conducted. Firstly, bottom sediments, suspended particulate matter and oyster samples were analysed for metals over three years in Sydney estuary. Correlations were investigated between oysters to sediments and SPM and a significant mismatch was observed between field and transplanted oysters, with strong regressions in the latter to fine sediments and SPM, but a lack in the former. Resuspension was replicated in the laboratory and a gradient of metal concentrations and resuspended loads were exposed to oysters in a two month mesocosm experiment. No relationship was determined between either variables to oyster metal bioaccumulation. To confirm either dissolved or particulate metal uptake, a radioisotope tracer study exposed oysters to gamma-emitting 65Zn, a first for an Australian bivalve species using 65Zn. The resulting biokinetic uptake and loss rates were used to construct a steady-state model and particulate sources were determined to be the greatest contributor. The mesocosm and radiotracer experiment results were used to formulate a novel, dynamic, coupled biokinetic-equilibrium model to investigate the mechanisms and processes governing oyster metal bioaccumulation. The coupled model concluded that dissolved organic matter commanded a dominant influence on metal bioaccumulation patterns for many metals by sequestering them and reducing their bioavailability. The present work demonstrated that dietary uptake of resuspended, contaminated sediments is unlikely to be a key source of metals to filter-feeding oysters.
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