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1
Clements, Katie. "Bacterial reservoirs in shellfish and shellfish harvesting waters." Thesis, Bangor University, 2013. https://research.bangor.ac.uk/portal/en/theses/bacterial-reservoirs-in-shellfish-and-shellfish-harvesting-waters(81ba795c-0d56-42b7-8a2b-9a90f7c96f50).html.
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Shellfish have been recognised as an important human food source since Roman times and are now routinely consumed by inhabitants across five continents. However, shellfish are also well known vectors for human illness as they are capable of bio-accumulating pathogenic micro-organisms from the wider environment within somatic tissues and hence, are capable of transferring these pathogens into the human food chain. Current European efforts to safeguard consumers include the routine bacteriological monitoring of shellfish tissues using E. coli as a proxy for potential pathogenic micro-organisms. The aims of this thesis were firstly, to identify and quantify the bacterial reservoirs present in commercial shellfish harvesting areas. Secondly, to determine the relative contribution of these reservoirs under different mitigation techniques, and thirdly, to examine the relationship between the bacterial and viral reservoirs present within shellfish tissues. A single commercial mussel (Mytilus edulis) bed was intensively surveyed to identify both spatial and temporal changes in the bacterial reservoir present within mussel tissues and to examine the relationship between the bacterial reservoir present within the mussel tissues and concentrations of bacteria present in the underlying sediment. This study concluded that the underlying sediments represented a greater bacterial reservoir than within the mussel tissues, however no spatial relationship between the two reservoirs was evident. In addition, we investigated the potential of epizoic organisms to act as a bacterial reservoir. The findings from this study demonstrated that epizoic barnacles contained more than 80% of the total coliform bacteria present and, as such, represent a previously unidentified, but significant bacterial reservoir in shellfish harvesting areas. Based on previous findings, the effect of standard mitigation techniques i.e. depuration and offshore relaying on the previously identified bacterial reservoirs were investigated. A standard 48 hour depuration treatment was shown to be effective in the reduction of indicator bacteria from shellfish tissues, but ineffective in reducing the bacterial content of epizoic organisms to beneath acceptable levels. Offshore relaying was shown to be an effective measure to reduce both bacterial and viral concentrations in shellfish tissues, however, these concentrations demonstrated no relationship with the bacterial content of the surrounding waters. Finally the relationship between the bacterial and viral content of shellfish tissues was examined and compared to modelled E. coli concentrations in the water surrounding a sewage outfall. No relationship between the bacterial and viral content of the shellfish was observed. This finding supports previous studies suggesting that bacterial indicators are poor surrogates for viral contamination of shellfish. However, interestingly the determined concentrations of norovirus within shellfish tissues were more closely correlated with the modelled predictions than the determined E. coli concentrations from the shellfish tissues. In conclusion, the bacterial reservoir within shellfish flesh may be over-shadowed by larger bacterial reservoirs present within the wider shellfish harvesting area. The interaction between these environmental bacterial reservoirs and the bacterial reservoirs within shellfish flesh remains largely unknown, and represents an area for further study, especially with regard to the impact of alternative environmental bacterial reservoirs on the bacterial content of shellfish destined for human consumption.
2
Mackenzie, Kimberley Jane. "Detection of male specific F+RNA bacteriophage in shellfish using recombinant antibody technology." Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources. Restricted: no access until July 1, 2012, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=26268.
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Stewart, Michael. "Biotoxins from New Zealand shellfish." Thesis, University of Canterbury. Chemistry, 1997. http://hdl.handle.net/10092/8607.
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New Zealand experienced its first recognised outbreak of shellfish poisoning around Northland in early 1993. The poisoning symdrome was characterised as neurotoxic shellfish poisoning (NSP) from the observed symptoms. The major causative toxins were isolated and characterised by the Japanese research groups of Professor Ishida (University of Shizuoka) and Professor Yasumoto (Tohoku University). The toxins were identified as brevetoxin B derivatives.
Diarrhetic shellfish poisoning (DSP) was suspected as responsible for further poisoning around this area. Yessotoxin (YTX), a suspect DSP toxin, was isolated as part of this research and is the first reported instance of YTX in New Zealand.
A stereochemical study was carried out on a desulfated YTX derivative. The results suggested anomalies in the reported conformation of YTX. Attempted synthesis of haptens of YTX for development of an ELISA is outlined in this thesis.
Another incident of shellfish contamination occurred around Foveaux Strait in early 1994. The toxicity was characterised by NSP symptoms in mice. The causative toxin, gymnodimine, was first reported by a Japanese research group, although independent parallel structure elucidation was carried out as part of this research.
The absolute stereochemistry of gymnodimine was solved by X-ray analysis of a synthetically modified derivative. Gymnodimine haptens were prepared for development of an ELISA. A chromatography based assay has been developed for the specific detection of gymnodimine in shellfish and alga. This work was modified from the extremely efficient isolation procedure for gymnodimine developed as part of this research.
4
Baker, Maria. "Fertilization success in commercial shellfish." Thesis, University of Southampton, 2001. https://eprints.soton.ac.uk/189935/.
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Merchant, Orelia Eleta. "Shellfish Culture Area Designation Protocol Development." W&M ScholarWorks, 1995. https://scholarworks.wm.edu/etd/1539617684.
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Hong, Haizheng. "Toxicological studies of paralytic shellfish toxins in mammalian systems /." View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?BIOL%202003%20HONG.
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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003.Includes bibliographical references (leaves 101-111). Also available in electronic version. Access restricted to campus users.
7
Selander, Erik. "Chemical ecology of paralytic shellfish toxin producing dinoflagellates /." Göteborg : Fiskebäckskil : Dept. of Marine Ecology, Göteborg University, Kristineberg ; Kristineberg Marine Research Station, 2007. http://www.loc.gov/catdir/toc/fy0804/2007440828.html.
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Hold, Georgina Louise. "The role of bacteria in paralytic shellfish poisoning." Thesis, University of Glasgow, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301622.
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Ho, Yam Tat. "The roles of bacteria in the production of paralytic shellfish toxins in two dinoflagellate cultures /." View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?BIOL%202003%20HO.
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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003.Includes bibliographical references (leaves 118-130). Also available in electronic version. Access restricted to campus users.
10
Zhao, Bin. "Larval biology and ecology of a non-indigenous species, the slipper limpet crepidula onyx /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?BIOL%202002%20ZHAO.
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Robbins, John A. "Stable isotopes, marine paleoclimates, and human subsistence on California's Channel Islands." Ann Arbor, Mich. : ProQuest, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1442835.
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Thesis (M.S. in Geology)--S.M.U., 2007.Title from PDF title page (viewed Mar. 18, 2008). Source: Masters Abstracts International, Volume: 45-05, page: 2387. Adviser: Robert Gregory. Includes bibliographical references.
12
Madhavi, B. "Molecular characterisation of bacterial pathogens of finfish and shellfish." Thesis, Central Marine Fisheries Research Institute, 1999. http://eprints.cmfri.org.in/11076/1/Madhavi%20B..pdf.
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Microbial molecular genetics is gaining popularity in recent times as an essential tool in the classification of the microbes. Numerical taxonomy of bacteria, unless supported by molecular taxonomy is not acceptable in the modem times. Proper understanding o f the DNA and protein profiles o f bacteria can be used as an efficient and sensitive tool for rapid identification o f bacteria whereas, the conventional methods are tiresome, time consuming and not fit for mass scale screening o f bacteria.
13
Burgess, Vanessa Anne, and n/a. "Toxicology Investigations With The Pectenotoxin-2 Seco Acids." Griffith University. School of Public Health, 2003. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20030905.090222.
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Pectenotoxins (PTXs) are a group of large cyclic polyether compounds associated with diarrhetic shellfish poisoning (DSP) as they are often found in combination with other DSPs such as okadaic acid (OA) and dinophysis toxins (DTXs) in shellfish. Although classified and regulated with the DSPs, there is debate over whether these toxins should be classified with DSP toxins. To date, ten different analogues of PTXs have been identified from shellfish and algae, and of these, the pectenotoxin-2 seco acids (PTX2-SAs) are of particular interest as they have previously been implicated in a shellfish poisoning incident in Australia, but relatively little was known of their toxicology. One such incident occurred in December 1997, when approximately 200 people were reported with severe diarrhoetic shellfish poisoning in Northern New South Wales (NSW). Analysis of the shellfish associated with this incident revealed relatively high PTX2-SA concentrations (approx. 300 micrograms/kg shellfish meat), with only trace amounts of pectenotoxin-2 (PTX2) and OA. Following this incident, PTX2-SAs were considered a health threat and guidelines were implemented in the absence of toxicological data, which has caused a great economic burden to shellfish industries around the globe, in particular to Australia, New Zealand and Ireland. Such regulation created in the absence of scientific data demonstrated the need to determine the toxicology of PTX2-SAs in commercial shellfish. Thus a comprehensive study on the toxicology and possible health implications of the PTX2-SAs in Australian shellfish was conducted. PTX2-SAs were isolated in different batches from shellfish (pipis, oysters and mussels) and from algal bloom samples of Dinophysis caudata. Toxin extraction was conducted with several purification stages and chemical analysis was performed with high-performance liquid chromatography coupled to a tandem mass spectrometer (HPLC-MS/MS). The chemical stability of the PTX2-SAs was investigated to ensure consistency of doses between toxicology experiments. Acute dosing studies with mice were then performed and included toxicopathology investigations with light microscopy and electron microscopy, in addition to toxin distribution studies and investigation of in vivo lipid peroxidation. In vitro studies with HepG2 cells included cytotoxicity assays, cell cycle investigations using flow cytometry and gene expression profiling of cells exposed to PTX2-SAs employing cDNA microarray technology. Acute pathology studies demonstrated that the PTX2-SAs do not cause the characteristic symptoms or lesions associated with DSP toxins. No diarrhoea was observed at any dose level in mice and no deaths occurred up to the maximum dosing level of 1.6mg/kg PTX2-SA. Only one batch of PTX2-SA extract produced toxic lesions characteristic of a DSP toxin (batch 1-pilot study) but after follow up studies, it was determined that this first batch of shellfish most likely contained an additional unidentified shellfish toxin or contaminant that co-extracted with PTX2-SAs during toxin isolation and purification procedures. This finding highlighted the importance of supporting the inclusion of the mice bioassay in procedures for shellfish toxin testing to enable detection of new toxins, and also highlighted the importance of toxin purification for toxicology studies. A significant rise in malondialdehyde excretion was observed within 24 hours of dosing mice, indicating that the PTX2-SAs may cause damage by lipid peroxidation in vivo. In vitro studies showed HepG2 cells to have cell cycle and gene expression changes within 24 hours of a dose of 800ng/mL PTX2-SAs. Cell cycle arrest was observed at the G2/M checkpoint and gene expression changes included alterations in genes involved in cell cycle control, lipid metabolism and transport, lipid genesis and trace metal transport. Many genes involved in DNA repair processes were moderated at the 24 hour point, but as no apoptosis was observed up to 72 hours post dosing it is a promising indication that any DNA damage that may have been caused by the administration of PTX2-SAs was not lethal, and was able to be repaired. In light of the information provided by toxicology investigations in this PhD, with particular reference to evidence of in vivo lipid peroxidation by raised levels of MDA in mouse urine, and changes in cell cycle distribution and gene expression in a cultured human cell line, it is concluded that there is potential for these toxins to induce biological changes in mammalian cells in vivo and in vitro, and hence potential for PTX2-SAs to cause health effects in humans. During the course of this three-year study, developments in techniques for shellfish toxin identification within our laboratories have revealed that the shellfish responsible for the 1997 NSW poisoning incident contained significant concentrations of okadaic acid acyl esters that were not detected at the time of the NSW incident. Although reportedly less toxic than okadaic acid itself, the OA ester concentrations present may have been sufficient to cause the observed symptoms. It is also theorized that these esters could be hydrolyzed in the human gastro-intestinal tract to release okadaic acid. In the light of this new evidence and with no pathology lesions or symptoms of diarrhoea being observed in PTX2-SA dosing studies with mice, we now believe these OA acyl esters to be the causative agent in the 1997 NSW DSP incident and not the PTX2-SAs. Nothing is currently known of the chronic toxicology of PTX2-SAs and thus their potential implications to public health in the long term cannot determined. The toxicology investigations in this thesis were acute studies, and it has not been established if the observed changes could be repaired or returned within normal limits without the manifestation of illness or disease occurring. Utilizing the acute toxicology information in this thesis, a health risk assessment for consumption of PTX2-SA contaminated shellfish was performed. This risk assessment, employing numerous safety factors essential for an incomplete data set, produced guideline values that are lower than the current recommend concentrations. To date, there has been no solid evidence that PTX2-SAs cause illness in humans all documented incidents involving the PTX2-SAs have also included other DSP contaminants that are known to cause human illness. Pathology has not unequivocally been demonstrated in animal studies and thus, in consideration of the epidemiological evidence, PTX2-SAs cannot be considered as high a risk to public health as was previously thought. For the reasons discussed above, and weighing up risk-benefit considerations of the economic burden the current guideline values are causing to shellfish industries around the globe, it is recommended that levels of PTX2-SAs be monitored in recognition of the precautionary principle, but no longer regulated as tightly with other DSPs until such a time that toxicological or epidemiological evidence can prove that the PTX2-SAs are a DSP and are a more considerable threat to human health than has been indicated by toxicology studies in this thesis. This study has produced a substantial amount of acute toxicology data and has provided a good basis for future chronic toxicology investigations with the PTX2-SAs for regulatory purposes.
14
Burgess, Vanessa Anne. "Toxicology Investigations With The Pectenotoxin-2 Seco Acids." Thesis, Griffith University, 2003. http://hdl.handle.net/10072/365382.
Full textAbstract:
Pectenotoxins (PTXs) are a group of large cyclic polyether compounds associated with diarrhetic shellfish poisoning (DSP) as they are often found in combination with other DSPs such as okadaic acid (OA) and dinophysis toxins (DTXs) in shellfish. Although classified and regulated with the DSPs, there is debate over whether these toxins should be classified with DSP toxins. To date, ten different analogues of PTXs have been identified from shellfish and algae, and of these, the pectenotoxin-2 seco acids (PTX2-SAs) are of particular interest as they have previously been implicated in a shellfish poisoning incident in Australia, but relatively little was known of their toxicology. One such incident occurred in December 1997, when approximately 200 people were reported with severe diarrhoetic shellfish poisoning in Northern New South Wales (NSW). Analysis of the shellfish associated with this incident revealed relatively high PTX2-SA concentrations (approx. 300 micrograms/kg shellfish meat), with only trace amounts of pectenotoxin-2 (PTX2) and OA. Following this incident, PTX2-SAs were considered a health threat and guidelines were implemented in the absence of toxicological data, which has caused a great economic burden to shellfish industries around the globe, in particular to Australia, New Zealand and Ireland. Such regulation created in the absence of scientific data demonstrated the need to determine the toxicology of PTX2-SAs in commercial shellfish. Thus a comprehensive study on the toxicology and possible health implications of the PTX2-SAs in Australian shellfish was conducted. PTX2-SAs were isolated in different batches from shellfish (pipis, oysters and mussels) and from algal bloom samples of Dinophysis caudata. Toxin extraction was conducted with several purification stages and chemical analysis was performed with high-performance liquid chromatography coupled to a tandem mass spectrometer (HPLC-MS/MS). The chemical stability of the PTX2-SAs was investigated to ensure consistency of doses between toxicology experiments. Acute dosing studies with mice were then performed and included toxicopathology investigations with light microscopy and electron microscopy, in addition to toxin distribution studies and investigation of in vivo lipid peroxidation. In vitro studies with HepG2 cells included cytotoxicity assays, cell cycle investigations using flow cytometry and gene expression profiling of cells exposed to PTX2-SAs employing cDNA microarray technology. Acute pathology studies demonstrated that the PTX2-SAs do not cause the characteristic symptoms or lesions associated with DSP toxins. No diarrhoea was observed at any dose level in mice and no deaths occurred up to the maximum dosing level of 1.6mg/kg PTX2-SA. Only one batch of PTX2-SA extract produced toxic lesions characteristic of a DSP toxin (batch 1-pilot study) but after follow up studies, it was determined that this first batch of shellfish most likely contained an additional unidentified shellfish toxin or contaminant that co-extracted with PTX2-SAs during toxin isolation and purification procedures. This finding highlighted the importance of supporting the inclusion of the mice bioassay in procedures for shellfish toxin testing to enable detection of new toxins, and also highlighted the importance of toxin purification for toxicology studies. A significant rise in malondialdehyde excretion was observed within 24 hours of dosing mice, indicating that the PTX2-SAs may cause damage by lipid peroxidation in vivo. In vitro studies showed HepG2 cells to have cell cycle and gene expression changes within 24 hours of a dose of 800ng/mL PTX2-SAs. Cell cycle arrest was observed at the G2/M checkpoint and gene expression changes included alterations in genes involved in cell cycle control, lipid metabolism and transport, lipid genesis and trace metal transport. Many genes involved in DNA repair processes were moderated at the 24 hour point, but as no apoptosis was observed up to 72 hours post dosing it is a promising indication that any DNA damage that may have been caused by the administration of PTX2-SAs was not lethal, and was able to be repaired. In light of the information provided by toxicology investigations in this PhD, with particular reference to evidence of in vivo lipid peroxidation by raised levels of MDA in mouse urine, and changes in cell cycle distribution and gene expression in a cultured human cell line, it is concluded that there is potential for these toxins to induce biological changes in mammalian cells in vivo and in vitro, and hence potential for PTX2-SAs to cause health effects in humans. During the course of this three-year study, developments in techniques for shellfish toxin identification within our laboratories have revealed that the shellfish responsible for the 1997 NSW poisoning incident contained significant concentrations of okadaic acid acyl esters that were not detected at the time of the NSW incident. Although reportedly less toxic than okadaic acid itself, the OA ester concentrations present may have been sufficient to cause the observed symptoms. It is also theorized that these esters could be hydrolyzed in the human gastro-intestinal tract to release okadaic acid. In the light of this new evidence and with no pathology lesions or symptoms of diarrhoea being observed in PTX2-SA dosing studies with mice, we now believe these OA acyl esters to be the causative agent in the 1997 NSW DSP incident and not the PTX2-SAs. Nothing is currently known of the chronic toxicology of PTX2-SAs and thus their potential implications to public health in the long term cannot determined. The toxicology investigations in this thesis were acute studies, and it has not been established if the observed changes could be repaired or returned within normal limits without the manifestation of illness or disease occurring. Utilizing the acute toxicology information in this thesis, a health risk assessment for consumption of PTX2-SA contaminated shellfish was performed. This risk assessment, employing numerous safety factors essential for an incomplete data set, produced guideline values that are lower than the current recommend concentrations. To date, there has been no solid evidence that PTX2-SAs cause illness in humans – all documented incidents involving the PTX2-SAs have also included other DSP contaminants that are known to cause human illness. Pathology has not unequivocally been demonstrated in animal studies and thus, in consideration of the epidemiological evidence, PTX2-SAs cannot be considered as high a risk to public health as was previously thought. For the reasons discussed above, and weighing up risk-benefit considerations of the economic burden the current guideline values are causing to shellfish industries around the globe, it is recommended that levels of PTX2-SAs be monitored in recognition of the precautionary principle, but no longer regulated as tightly with other DSPs until such a time that toxicological or epidemiological evidence can prove that the PTX2-SAs are a DSP and are a more considerable threat to human health than has been indicated by toxicology studies in this thesis. This study has produced a substantial amount of acute toxicology data and has provided a good basis for future chronic toxicology investigations with the PTX2-SAs for regulatory purposes.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Public Health
Faculty of Health Sciences
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Cerda, Ruben Osvaldo Bustos. "Microbial extraction of chitin from prawn shell waste." Thesis, Queen's University Belfast, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337646.
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McKelvey, Fionnuala. "Population ecology and fisheries management of the native oyster, Ostrea edulis L. in Lough Foyle." Thesis, University of Ulster, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241729.
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Bell, Arran M. "On the validity of archaeological shellfish metrics in coastal California." [Chico, Calif. : California State University, Chico], 2009. http://hdl.handle.net/10211.4/161.
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John, E. H. "Growth dynamics and physiology of paralytic shellfish toxin producing dinoflagellates." Thesis, Swansea University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637432.
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Studies on the growth dynamics and physiology of the paralytic shellfish toxin producing dinoflagellates Alexandrium fundyense, A. minutum and Gymnodinium catenatum were conduced under a number of different nutrient regimes, light, temperature and salinity levels. G. catenatum was very slow to respond to N-refeeding, with relatively low internal amino acid concentrations, a low glutamine:glutamate ratio, and a stable toxin content, showing little variation with N- and P-limitation or with decreased salinity. In contrast Alexandrium sp. respond to N-refeeding with an increased internal amino acid pool, an increased glutamine: glutamate ratio, especially with ammonium as a N-source, and an increased toxin content. P-limitation in A. fundyense leads to a significant increase in the toxin content but only when cells are also N-limited. Sub-optimal temperature and light levels lead to decreased growth rates: low temperature results in larger cells and an increased toxin content in A. fundyense, whilst the effect of low light on A. minutum cells varies with the N-source available. The N-uptake kinetics of G. catenatum revealed that the maximum uptake rates (Vmas) and half-saturation constants (Ks) for transport were higher for ammonium when compared with nitrate. In A. funyense values of Ks were similar at 1 μM for both nitrate and ammonium whilst Vmax for the latter was up to 5-times greater. A. fundyense was shown to be able to utilize organic-N in the form of dissolved free amino acids. Maximum uptake rates of 0.85 pmol cell-1 h-1 occurred during exponential growth and differed from the uptake capabilities of other phytoplankton in that uptake was not enhanced by N- or C-stress. A preliminary model is presented and is capable of simulating the relationship between N-refeeding and P-limitation and cellular toxin content in Alexandrium sp.
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Chan, Hon-wing, and 陳漢榮. "Food poisoning outbreaks in Hong Kong resulting from shellfish contamination." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1996. http://hub.hku.hk/bib/B31253349.
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Taylor, Gareth Foley. "Management of Sand Beaches for the Protection of Shellfish Resources." Thesis, University of Canterbury. Biological Sciences, 2013. http://hdl.handle.net/10092/8207.
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Exposed sand beaches are increasingly under pressure from human population growth and recreation. Activities, such as vehicle driving and horse riding, can pose a significant threat to specialist fauna living in the sediment. Few studies have evaluated how vehicles affect sand beach fauna and none have examined the impacts of horse users on burrowing bivalves.
The research questions addressed were: do vehicles and/or horses on sand beaches impact on intertidal shellfish populations? Following on from this, can management policies mitigate any negative impacts from such activities on sand beaches? This research required an interdisciplinary approach utilising methodologies from coastal geomorphology, biological science and management. The intertidal distribution of the New Zealand surfclam Paphies donacina (southern tuatua) determined seasonally on six exposed surf beaches along Pegasus Bay. The impacts of vehicle and horse users on shellfish survival were experimentally investigated, and novel in situ methods were developed to examine the effects of horses on bivalve survival.
Intertidal tuatua were small (< 30 mm) and shallowly buried. Found approximately 30 m below the last high tide line, they may be exposed to vehicle and horse users. There was a positive linear relationship between the number of vehicle passes and tuatua mortality (% tuatua mortality = 4.8 + 0.23 x number of vehicle passes). On average, horse riding resulted in 36.9% tuatua mortality within a single hoof print, but walking resulted in lower mortality than trotting or galloping. Extrapolative modelling predicted that the long-term presence of these users would be highly detrimental to shellfish. Reducing the temporal frequency and spatial extent of vehicle and horse users on sand beaches could decrease shellfish mortality. The thesis results were used to evaluate current management techniques and provide management options to minimise the potential impacts of beach users on shellfish resources.
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Henshilwood, Kathleen. "The detection of food-borne viruses in bivalve molluscan shellfish." Thesis, University of Surrey, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367689.
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Li, Pilong. "Radiobiosynthesis of paralytic shellfish toxins in the dinoflagellate alexandrium tamarense /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?BIOL%202002%20LI.
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Chan, Hon-wing. "Food poisoning outbreaks in Hong Kong resulting from shellfish contamination /." Hong Kong : University of Hong Kong, 1996. http://sunzi.lib.hku.hk/hkuto/record.jsp?B17457762.
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Neikirk, Robert Charles. "An Investigation of Impediments to Commercial Shellfish Mariculture in Virginia." W&M ScholarWorks, 1990. https://scholarworks.wm.edu/etd/1539617609.
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A nationwide survey of shellfish mariculturists was used in conjunction with a literature review and review of state and federal laws and regulations, to identify impediments to commercial shellfish mariculture development. The results of the survey and reviews were utilized to identify likely impediments to commercial shellfish mariculture in Virginia and to develop recommendations to address the identified impediments, should Virginia wish to pursue efforts to enhance development of this industry. This study suggests there are state laws, regulations, and policies which act as impediments to commercial shellfish mariculture development in Virginia. Mar,y of the identified regulatory impediments result from the applicability of laws and regulations designed to manage and protect the natural resources and more traditional uses of the coastal zone. Because this study relies heavily on subjective input from individuals representing the mariculture industry and did not involve individuals who may have attempted to enter the industry and failed, it may not accurately identify all of the actual impediments to the industry's development. However, the study should provide valuable input into any comprehensive state effort to enhance shellfish mariculture development in the Commonwealth of Virginia.
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Li, Pui-lin Jennifer, and 李佩蓮. "Aspects of bacteriology/virology of shellfish in relation to public health." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1997. http://hub.hku.hk/bib/B31253799.
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McNeish, Alexander Samuel. "Methylated cyclic organochlorines in fish and shellfish from the Mersey Estuary." Thesis, University of Liverpool, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260324.
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Li, Pui-lin Jennifer. "Aspects of bacteriology/virology of shellfish in relation to public health /." Hong Kong : University of Hong Kong, 1997. http://sunzi.lib.hku.hk/hkuto/record.jsp?B18734261.
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Peck, Lauren. "Feasibility of shellfish reef restoration in a south-western Australian estuary." Thesis, Peck, Lauren (2019) Feasibility of shellfish reef restoration in a south-western Australian estuary. Honours thesis, Murdoch University, 2019. https://researchrepository.murdoch.edu.au/id/eprint/52310/.
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With 85% of oyster reefs lost around the world within the last 130 years, these reefs are now one of the most threatened marine habitats in the world and in Australia less than 10% of naturally occurring oyster reefs remain. Shellfish reefs provide a range of services that promote healthy ecosystems, including water filtration, fish production and shoreline erosion. In estuaries, these services are extremely important as human activities are increasing degrading these environments. Thus, shellfish reefs can aid in restoring ecosystem functioning of an estuary while providing additional ecosystem services. The aim of this study was to determine the feasibility of a number of shellfish reef options for the Peel-Harvey Estuary in south-western Australia. This first involved exploring the historical and current distributions of shellfish to elucidate whether shellfish reefs existed in the Peel-Harvey Estuary and to identify a suite of candidate species.
A bioclimatic modelling approach was then used to elucidate the suitability of five native Australian oyster species to the environmental conditions that occur in the Peel-Harvey Estuary, the largest estuary in south-western Australia. Laboratory tank trials were then used to validate the results of that model, in which the two most suitable species, i.e. Ostrea angasi and Saccostrea glomerata, were exposed, for two months, to the extremes in water temperature and salinity that occur in the Peel-Harvey Estuary during summer (26◦C and 48ppt) and winter (15◦C and 14ppt) and their survival, body condition index (BCI) and behaviour (valve activity) monitored.
The probability of survival (S) over the duration of the study was lowest for O. angasi in the summer (S=0.0) and winter treatments (S=0.18), which both differed significantly (P<0.001) from the control group (marine condition), and were consistent with the salinity in the winter and summer treatments falling outside previously recorded tolerance thresholds. In contrast, S. glomerata had a high probability of survival in winter (S=0.98), and ~50% survived the extreme summer conditions. A significant difference of valve activity was found for O. angasi between the three conditions (P<0.05), however, only a significant difference in valve activity for S. glomerata was found between the marine and summer (P<0.05), and marine and winter conditions (P<0.05). Overall, body condition index (BCI) did not differ significantly (P>0.05) before or among treatments. The results of the bioclimatic model and survival analyses suggest that S. glomerata was the most suitable candidate for shellfish reef restoration in the Peel-Harvey Estuary, given in particular the extremes that occur in salinity. Further work is required to determine the most suitable areas in the estuary that would maximise survival and growth and thus where such reefs would have a positive impact on the overall health and resilience of the Peel-Harvey Estuary.
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Rahman, Mohammad Shamsur. "Molecular Characterization of Vibrio spp. in Shellfish using Multilocus Sequence Analysis." Doctoral thesis, Università degli studi di Padova, 2013. http://hdl.handle.net/11577/3423397.
Full textAbstract:
Fish and shellfish are the second largest source of protein for man after meat products and in some countries, such as Japan, constitute the main source of protein. In recent years, indigenous marine bacteria were responsible for 20% of all diseases and 99% of fatalities associated with the consumption of fishery products (Cozzi and Ciccaglioni, 2005). Among these, the main causes of diseases are some species of Vibrionaceae, which can cause gastroenteritis, especially after the consumption of fish products, raw or undercooked, from temperate and warm Seas. Vibrio is a very diverse genus responsible of different human and animal diseases. The accurate identification of Vibrio spp. is very important to assess the risks in regard to public health and diseases of aquatic organisms. Thus, analyses of population structure for a reliable bacteria characterization in different ecological environments are necessary. In particular, sequence based identification methods are preferable over classical biochemical approaches. In this study, a Multilocus Sequence Analysis scheme was developed on the basis of four housekeeping genes (gyrB, pyrH, recA and atpA) applied to 3 set of Vibrio strains (154 isolates from mollusks in 2007; 92 isolates from crustacean and 22 isolates form mollusks in 2011 ) and 29 reference strains. Concatenated sequences were used for phylogenetic and population analyses and the results were compared with biochemical identification tests (Alsina’s scheme). The phylogeny provided a good clustering, showing 15 clusters and 6 single strains in the first set of strains; 10 clusters and 4 singletons in second set; and 4 clusters and 4 singletons in the third set of strains. The population analysis highlighted 17 subpopulations in first set and 12 subpopulations in second set of Vibrio strains that were well supported by phylogeny with few exceptions. Overestimations of risk due to biochemical identification have been found for V. parahaemolyticus and V. vulnificus and no V. cholerae strains were identified. The false negative results of Alsina’s scheme need to be considered as it might represent a potential public health risk. These findings highlight the need of a rapid and robust identification of shellfish associated foodborne Vibrio spp. and, in addition, the connection of environmental information to genetic data could enhance the Vibrio spp. characterization.
Second part of the study gave special emphasis on the species Vibrio parahaemolyticus, a potential emerging pathogen in the North Adriatic Sea. Pathogenic strains of V. parahaemolyticus represent one of the main causes of foodborne gastroenteritis, especially in Asia and USA (Su and Liu, 2007). The study examined 160 strains isolated from 43 edible mollusks sampled between January and October 2011, identified biochemically as Vibrio parahaemolyticus in the Food Microbiology laboratory of Istituto Zooprofilattico (IZSVe). The strains were characterized for the presence of genes typical for the species Vibrio parahaemolyticus (toxR and tlh) in order to confirm the biochemical identification and virulence genes (tdh and trh). Dubious or misidentified strains were subjected to MLSA (Multilocus Sequence Analysis) by evaluating the sequence of 4 housekeeping genes. Finally, 102 Vibrio parahaemolyticus strains were analyzed by the MLST protocol: portions of 7 genes (dnaE, gyrB, recA, dtdS, pntA, pyrC and tnaA) were sequenced and concatenated. With the obtained MLST information phylogenetic analyses were performed to determine the relationships between the different strains isolated in this study and secondly, any links with worldwide isolates. All strains of V. parahaemolyticus were found positive for toxR and tlh, no strain was tdh positive, while 6 strains had the positive reaction for trh gene. 72 non-redundant (63 new) STs were identified. A total of 54 clonal groups were highlighted, in which 17 are clonal complex. Two distinct populations of V. parahaemolyticus were marked by phylogenetic, structure and recombination analyses. The main result is that despite the high percentage of positive samples for V. parahaemolyticus, only a few strains were potentially pathogenic for humans. However, some possible genetic relationships with strains can emerge from a comparative study with the STs in the world database. The characterization could help to identify suspect genotypes and thus clarify the dynamics of the spread of potentially pathogenic strains.I prodotti ittici sono la seconda fonte di proteine per l’alimentazione dell'uomo e in alcuni Paesi, quali il Giappone, ne costituiscono la principale fonte. Negli ultimi anni, i batteri marini della flora indigena sono risultati responsabili del 20% delle malattie nell’uomo e del 99% dei decessi derivati dal consumo dei prodotti della pesca. Tra questi, le principali cause di malattie sono da ascrivere ad alcune specie di Vibrionaceae in particolare al genere Vibrio, che possono causare gastroenteriti, soprattutto a seguito di consumo di prodotti crudi o poco cotti, provenienti da mari temperati e caldi. L'identificazione accurata dei batteri appartenenti al genere Vibrio risulta quindi molto importante per valutare i rischi in materia di salute pubblica e per l’identificazione puntuale delle malattie degli organismi acquatici. Risulta quindi necessario sviluppare ed applicare metodi affidabili che possano caratterizzare le specie di vibrioni residenti nei prodotti commercializzati (es. molluschi bivalivi e crostacei). In particolare, i metodi di identificazione basati sull’analisi delle sequenze geniche sono preferibili rispetto ai classici approcci biochimici. In questo studio è stato sviluppato uno schema MLSA Multilocus Sequence Analysis impiegando quattro geni housekeeping (gyrB, pyrH, recA e atpA), tale schema è stato valutato in 3 differenti data set di ceppi (154 isolati da molluschi nel 2007; 92 isolati di crostacei e 22 da molluschi isolati nel 2011) e 29 ceppi di riferimento e Type strain. I concatenameri sono stati utilizzati per le analisi filogenetiche e per gli studi di popolazione dei Vibrio isolati, confrontando al contempo i risultati dell’identificazione di specie con i test biochimici (schema di Alsina) applicati di routine all’identificazione dei Vibrioni. L’analisi della struttura di popolazione mediante il software STRUCTURE e l’analisi filogenetica risultano concordi nell’assegnazione dei principali taxa evidenziando una simile clusterizzazione dei gruppi in sottopopolazioni. Al contrario, il confronto tra la classificazione mediante MLSA e i test biochimici ha evidenziato varie discrepanze tra le quali una sovrastima di ceppi classificati come V. parahaemolyticus e V. vulnificus. Al contempo alcuni ceppi di V. parahaemolyticus sono risultati falsi negativi. Questi riscontri potrebbero indicare una limitazione dell’utilizzo delle prove biochimiche adottate di routine alla classificazione dei Vibrio potenzialmente patogeni per l’uomo e tale riscontro si riflette in un possibile rischio per la salute pubblica. La seconda parte dello studio ha considerato nel dettaglio la caratterizzazione molecolare di V. parahaemolyticus. Questo batterio è oggi un patogeno emergente derivato dal consumo di prodotti ittici, infatti ceppi patogeni di V. parahaemolyticus rappresentano una delle principali cause di gastroenterite di origine alimentare, in particolare in alcuni paesi dell’Asia e negli Stati Uniti. Questo batterio, a causa di mutamenti ambientali e delle abitudini dei consumatori (consumo di prodotti crudi provenienti da aree contaminate) potrebbe rappresentare una problematica igienico sanitaria anche nel Mare Adriatico settentrionale. In questa parte dello studio sono stati esaminati 160 ceppi isolati da 43 campioni di molluschi commestibili campionati tra gennaio e ottobre 2011 e identificati a livello biochimico dal laboratorio di microbiologia dell’Istituto Zooprofilattico Sperimentale delle Venezie (IZSVe). I ceppi sono stati caratterizzati per la presenza dei marker genici specie specifici (toxR e tlh - Vibrio parahaemolyticus) per confermare l'identificazione biochimica e quindi dei geni per i fattori di virulenza (tdh e trh). I ceppi risultati di dubbia o errata identificazione sono stati sottoposti a MLSA (Multilocus Sequence Analysis) valutando la sequenza dei 4 geni housekeeping. Infine tutti i ceppi risultati Vibrio parahaemolyticus (n° 102) sono stati analizzati mediante il protocollo MLST (http://pubmlst.org/vparahaemolyticus/.). Lo schema prevede l’analisi di sequenza di 7 porzioni geniche (dnaE, gyrB, recA, dtdS, pntA, pyrC and tnaA). I concatenameri ottenuti sono stati utilizzati nelle analisi bioinformatiche di popolazione per determinare le relazioni tra i diversi ceppi isolati in questo studio e, in seconda battuta, per evidenziare eventuali collegamenti con ceppi isolati a livello mondiale. Per quanto concerne i fattori di virulenza tutti i ceppi di V. parahaemolyticus sono risultati tdh negativi, mentre 6 ceppi hanno presentato la positività per il gene trh. Nel complesso sono stati identificati 72 profili ST non ridondanti, 63 dei quali di nuova attribuzione rispetto al database on-line. L’analisi clonale dell’intero database ha evidenziato la presenza di 54 gruppi clonali dei quali 17 risultano essere ascritti entro un complesso clonale. Le analisi di popolazione nel loro complesso delineano la presenza di due gruppi principali di V. parahaemolyticus. Dallo studio emerge che, nonostante sia stata riscontrata un’alta percentuale di campioni positivi per V. parahaemolyticus, solo pochi ceppi risultano potenzialmente patogeni per l'uomo. Tuttavia, alcune possibili relazioni genetiche con ceppi isolati da casi di gastroenteriti in varie parti del mondo emergono dallo studio comparativo con il database on-line. La caratterizzazione molecolare potrebbe aiutare a individuare genotipi sospetti e quindi chiarire la dinamica della diffusione di ceppi potenzialmente patogeni.
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Tylor, Timothy John Max. "Studies of Alexandrium sp. hypnocysts in Belfast Lough." Thesis, University of Westminster, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264001.
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Milne, Sarah Amelia. "The development of a sensitive and reliable molecular method for the detection of human pathogenic viruses in bivalve molluscs." Thesis, University of Aberdeen, 2002. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU159700.
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The overall aim of this project was to develop a sensitive, specific and reliable molecular assay for the detection of human pathogenic viruses in shellfish. In initial studies, 'viral surrogates' were used to evaluate two different assay formats, the reverse transcriptase-polymerase chain reaction-enzyme-linked immunosorbent assay (RT-PCR-ELISA) and the enzyme-labelled deoxynucleic acid-enzyme-linked coagulation assay (EDNA-ELCA). Each format was tested for ease of use, reliability and sensitivity, when compared with ethidium bromide gel detection. The RT-PCR-ELISA proved to be a successful alternative to ethidium bromide gel electrophoresis and studies involving virus detection in contaminated environmental samples were performed. The newly developed ELISA method was able to successfully detect enterovirus (EV) and Norwalk-like viruses (NLVs) in artificially, and naturally contaminated shellfish. In shellfish studies the ELISA had a detection sensitivity of 10-100, and 100-1000 TCID50 PV respectively, when a traditional elution/precipitation, and an immunocapture procedure were employed. The assay could also successfully detect virus in trout kidney samples, artificially contaminated with infectious pancreatic necrosis virus (IPNV), with detection sensitivities of 105, and 107 pfu reported when the elution/precipitation, and immunocapture procedures were used. In naturally contaminated shellfish samples, positive NLV and EV detection were achieved using the ELISA method. The ability of the ELISA to positively detect virus in environmental samples was compared to the TaqMan quantitative PCR system, an alternative detection method. Both methods were used to screen various contaminated environmental samples, including faeces and shellfish. The ELISA performed well, and unlike the TaqMan system no optimisation for each sample matrix tested was required. Overall the ELISA was shown to be a very robust and sensitive method. The technique was easily established in a new laboratory and no specialised equipment was required to perform the assay. The method has a high sample throughput, capable of screening 96 samples per run. Each sample takes only approximately 50 s to screen, making the technique extremely time efficient. The ELISA is a safe, quick, reliable technique, which has great potential for use as a standard virus detection method in a standard equipped laboratory.
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Mudunaivalu, Kusitino. "Evaluation of the Customary Fisheries Management of Shellfish in the Canterbury Region." Thesis, University of Canterbury. Biological Science, 2013. http://hdl.handle.net/10092/8179.
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During the last twenty years there has been a growing recognition of the need to protect shellfish populations all over the world. In New Zealand, customary management tools such as rehab (temporary closures) and mātaitai reserves provide an important management strategy, allowing shellfish populations to be managed and protected in coastal waters. This thesis examined the cultural management of shellfish in three Māori reserves in the Canterbury region, at Rāpaki, Port Levy and Kaikōura. The study measured the population characteristics of three key shellfish species that are important to Māori within the reserves and compared them with similar non-reserve sites. The shellfish populations were assessed using both scientific methods and cultural evaluations using traditional ecological knowledge (TEK). The scientific methods involved assessments of the abundance; size structure and condition index of pipis (Paphies australis), cockles (Austrovenus stutchburyi) and cats eyes (Turbo smaragdus). Semi-structured interviews were used to gather indigenous knowledge from kaumatua and kaitiaki on the abundance of shellfish and the state of their customary fisheries. The findings from the scientific research indicated that the customary reserves had higher shellfish abundance, larger individuals and higher abundance of harvestable size shellfish. The result of the cultural assessments suggested that there are enough shellfish in the three reserves to satisfy the customary needs of the communities. The kaitiaki acknowledged that the abundance and sizes of shellfish had been greater and larger in the past compared to the present. They have observed an increase in both size and abundance of shellfish since the customary reserves have been put in place. This study showed that scientific monitoring can provide important information about the structure and distribution of shellfish and that this is critical for sustainable management. The research findings indicated that scientific monitoring and TEK information can compliment each other for improved customary fishery management. The thesis research concluded that differences in shellfish populations between the reserves and non-reserve sites may be due, not only to the customary management, but a variety of complex factors that will require further monitoring. This research, however, provided baseline data about shellfish populations which can be used to monitor future changes. From a cultural perspective the customary management is conserving shellfish populations and therefore is successful at fulfilling the customary needs of the three Māori communities.
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Kostal, Jeri Elizabeth. "Assessment of Current Guidelines for Culinary Preparation Methods of Fish and Shellfish." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/49561.
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Consumers regularly decide to consume fish and shellfish raw or undercooked, which can cause foodborne illness due to product contamination or unsafe handling by the consumer. In order to be considered safe for consumption, intact fish and shellfish should be prepared to an internal temperature of 63"C, according to the 2009 FDA Food Code, with Salmonella spp. as the target organism. Focus groups (5 groups, 32 participants) were conducted to determine consumer beliefs and concerns regarding fish and shellfish safety and preparation. Transcripts of focus groups where coded for themes, which were then grouped into categories. Nine categories emerged including: experience, trust, confidence, quality of product, motivation, concerns, cooking procedures, cooking instructions, and knowledge. Emerging themes were used to help develop educational materials to increase consumer ability to properly prepare fish and shellfish. In a separate experiment, participants (n=6) cooked salmon (baked, broiled), tilapia (baked, broiled), and shrimp (broiled, boiled) according to cookbook-based directions. Internal temperatures of products were recorded, with 33.3% of products cooked to a temperature less than 63"C. A group training session was held, during which participants received additional visual and non-oral cues to determine when products were prepared to 63"C and safe food handling practices. After training, participants prepared the same products. Participants demonstrated improved food safety behaviors and were more successful at cooking products to temperatures "63"C (94.4% of products). Improved cooking instruction and educational materials may reduce the risk of foodborne illness from undercooked fish and shellfish.Master of Science in Life Sciences
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Kyriacou, Katharine. "The reinvestigation of Hoffman's/Robberg cave - the artefactual and shellfish assemblages, 2007." Master's thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/11871.
Full textAbstract:
Includes abstract.Includes bibliographical references (leaves 150-159).
This thesis documents the re-investigation of Hoffman's/Robberg Cave, a little known site located on the Robberg Peninsula near Plettenberg Bay on the southern Cape coast of South Africa. Previous excavations carried out at the site early in the twentieth century and again in the late 1950s are scantily documented. Furthermore, a large collection derived from Hoffman' s excavations, which I examined and catalogued in 2006, is only a selective sample of the archaeological remains from the site.
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Mohammadkhani, Ghasem. "Evaluation of Wet Spinning of Fungal and Shellfish Chitosan for Medical Applications." Thesis, Högskolan i Borås, Akademin för textil, teknik och ekonomi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-25537.
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The aim of this project was to address the food waste problem, particularly bread waste, to some extent by producing monofilaments obtained from wet spinning of fungal hydrogel through the cultivation of Rhizopus delemar on bread waste. The project had two phases. Firstly, the possibility of production of chitosan fiber with wet spinning (using different acids) was evaluated, the process was optimized, and then applied to the production of fungal fiber. Regarding first stage of the project, adipic acid, a non-toxic solvent with two carboxyl groups, was used as acting physical crosslinker between the chitosan chains, resulting in improving properties of the monofilaments. Adipic acid performance was compared with conventional solvents, such as citric, lactic, and acetic acids. By injecting chitosan solutions into a coagulation bath (EtOH or NaOH 1M or EtOH-NaOH or H2SO4-EtOH), monofilaments were formed. Scanning electron microscopy showed that uniform chitosan monofilaments with smooth surface were formed using adipic and lactic acids. In general, fibers obtained from adipic acid displayed higher mechanical strength (Young’s modulus of 4.45 GPa and tensile strength of 147.9 MPa) than that of monofilaments produced using conventional solvents. Fiber dewatering with EtOH before drying led to greater fiber diameter and lower mechanical strength. As the second stage of this study, Rhizopus delemar was cultivated on bread waste in shake flasks and 1.3 M3 bioreactor. While different combinations of ground bread and K2HPO4 was used as the substrate for shake flask cultivations, white bread waste without K2HPO4 was utilized for scaling up the process, mostly due to the Glucosamine (GlcN) and N-acetyl-glucosamine (GlcNAc) content in the fungal cell wall. GlcN and GlcNA content obtained from ground bread was remarkably higher than that of obtained from combinations of ground bread and K2HPO4 as the substrate. Cultivation in 1.3 M3 bioreactor resulted in about 36 kg wet biomass with a mean of 14.88% dry weight, indicating 5.95 g biomass/L. The biomass yield of 0.15 g dry biomass/g dry bread was achieved. Alkali insoluble material (AIM) was obtained by alkali treatment of biomass. Fungal hydrogel was prepared by adding adipic and lactic acid to AIM, followed by grinding treatment. While hydrogels treated with lactic acid showed better spinnability and gelling ability, the one from adipic acid was not uniform to be wet spun. Considering hydrogels treated with lactic acid, the optimum grinding cycle for more spinnable hydrogel was 6 negative cycles, contributing to the fibers with the tensile strength of around 82 MPa. Such fibers showed antibacterial property against Escherichia coli, making them as a good option for suture applications. However, further in vitro and in vivo trials are essential to test the fungal fiber for such applications.
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Maus, Charles J. "Biology and ecology of deployed shellfish habitats in the Swan-Canning Estuary." Thesis, Maus, Charles J. (2020) Biology and ecology of deployed shellfish habitats in the Swan-Canning Estuary. Honours thesis, Murdoch University, 2020. https://researchrepository.murdoch.edu.au/id/eprint/59578/.
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Large extents of shellfish reefs have become degraded around the world as a result of anthropogenic activities to the point where such reefs are functionally extinct in some regions. Due to the ecosystem services provided by these biogenic habitats, there has recently been a concerted effort to restore shellfish reefs, particularly in Australia. While oysters have traditionally been used as a candidate species, the Mediterranean Mussel Mytilus galloprovincialis is gaining popularity and provides a similar suite of ecosystem services to oysters. As part of a pilot program, shellfish habitats, each comprising translocated M. galloprovincialis seeded onto 100 wooden stakes, were deployed at three sites in Melville Water in the Swan-Canning Estuary (Western Australia). The aims of this study where to; 1) investigate the mortality, body condition and growth of the translocated M. galloprovincialis; 2) compare the characteristics of fish fauna at the shellfish reef habitats and nearby unstructured (control) habitats and 3) determine the benthic macroinvertebrate and tunicate species associated with the shellfish habitat.
The mortality of M. galloprovincialis was high at all three sites. This was attributed to poor environmental conditions in offshore waters of Melville Water, compounded by stress associated with translocation, their spawning activity, and fouling by ascidians. Seasonally adjusted von Bertalanffy growth models best explained the growth of M. galloprovincialis and growth was rapid, with individuals attaining ~50 mm within their first year. This is likely due to the high phytoplankton availability in the Swan-Canning Estuary.
The shellfish habitats harboured a significantly different fish faunal composition compared to nearby unstructured habitats (sandy areas), with many species observed only at shellfish sites or in greater densities. The increased abundances of zoobenthivores on the shellfish habitats suggest they are utilising the invertebrate prey communities associated with the structure as a food source. The invertebrate community varied spatially among the three sites and over time. A suite of non-native ascidians rapidly colonised the stakes along with the mussels, which, in turn, supported many small crustaceans.
Given the importance of shellfish restoration globally, and the aim to undertake large-scale projects to provide such habitats in south-western Australian estuaries, the results of this study will increase the understanding of the biology of M. galloprovincialis and help elucidate how faunal communities respond and utilise shellfish habitats. The results of this pilot study will assist in the planning of future mussel reef restoration projects, in particularly those under development in southern Australia.
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Huang, Jie. "Tidal Wetland Contributions to Fecal Coliform Loads in Shellfish Growing Waters by Analysis of Model Prediction Discrepancy." W&M ScholarWorks, 2005. http://www.vims.edu/library/Theses/Huang05.pdf.
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Higman, Wendy Ann. "The distribution and toxicity of Alexandrium of the north east coast of Britain." Thesis, University of Westminster, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339249.
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Joyce, Linda Britt. "An investigation into the occurrences of harmful algal blooms in Scapa Flow, Orkney." Thesis, Heriot-Watt University, 2001. http://hdl.handle.net/10399/1137.
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Harper, Terry L. "Improved methods of detection for the difficult to identify marine toxin, Okadaic acid /." Electronic version (PDF), 2005. http://dl.uncw.edu/etd/2005/harpert/terryharper.pdf.
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Pate, Susan Elizabeth. "Impacts of the toxic dinoflagellate Alexadrium monilatum on three ecologically important shellfish species." NCSU, 2006. http://www.lib.ncsu.edu/theses/available/etd-03062006-182116/.
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Little is known about interactions between shellfish and Alexandrium monilatum (Howell) Balech, a toxigenic dinoflagellate that forms blooms mostly in the Gulf of Mexico. Toxic A. monilatum produces endotoxins with hemolytic and neurotoxic properties, and has been linked to major fish and invertebrate kills. The responses of three ecologically important shellfish species to A. monilatum (toxic strain AMO3) were experimentally assessed. In the first set of experiments, grazing studies were conducted with adult and juvenile eastern oysters (Crassostrea virginica Gmelin), northern quahogs (Mercenaria mercenaria Linnaeus), and green mussels (Perna viridis Linnaeus), which inhabit areas where A. monilatum blooms occur. Clearance rates of each shellfish species were depressed when exposed to toxic A. monilatum (bloom density of ~550 cells ml-1) alone or with nontoxic Instant Algae® Pavlova, in comparison to clearance rates of control animals fed benign cryptophyte algae. There was also a reduction in the clearance rate of adult and juvenile C. virginica and P. viridis, as well as juvenile M. mercenaria exposed to A. monilatum, in comparison to control animals that were exposed to a nontoxic strain of a dinoflagellate of similar size, Alexandrium tamarense (clone CCMP115). Exposure to toxic A. monilatum significantly decreased shellfish valve gape in adult P. viridis and C. virginica. Intact A. monilatum cells were found within shellfish feces, but A. monilatum cells did not divide following passage through the gut. In the second set of experiments, survival of larval M. mercenaria and C. virginica was tested when the larvae were exposed to A. monilatum as intact cells, cells held in dialysis tubing, or sonicated cells. Survival of larvae was significantly less when exposed to sonicated A. monilatum, in comparison to survival of control larvae that were tested with nontoxic A. tamarense. Overall, these data indicate that A. monilatum blooms can adversely affect survival of some shellfish species by reducing clearance rate and valve gape, affecting food intake, and inducing larval mortality.
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Conn, Ailsa. "The importance of Norovirus and Cadmium in Shellfish and implications to human health." Thesis, University of Canterbury. Biological Science, 2010. http://hdl.handle.net/10092/4706.
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Shellfish are an important food source however they are known to harbour bacteria, viruses and toxic chemicals that can be detrimental to their human consumers. Oysters have been associated with the gastroenteritis virus Norovirus. New Zealand has some of the highest cases of foodborne illness in the western world.
This study investigated a possible link between periods of high rainfall and reported Norovirus outbreaks in four major cities in New Zealand (Auckland, Wellington, Christchurch and Dunedin) as well as national data. Norovirus is a highly infectious foodborne illness. Outbreaks of norovirus have been linked to the consumption of shellfish, and in particular oysters. Norovirus virions can enter the aquatic environment via sewage as a result of human shedding of the virus. This investigation into rainfall and Norovirus outbreaks found no statistically significant relationship, in a monthly or season setting.
In addition the relationship between environmental cadmium levels and exposure levels in New Zealand was investigated through meta-analysis. Cadmium is a heavy metal commonly associated with the mining of copper and zinc ores. It is found naturally in the environment, in air land and oceans Increased exposure to cadmium is known to have a number of serious detrimental health effects, in particular this study investigates cadmiums immunosuppressive properties. Concentrations in New Zealand were compared with Canada, Italy and the UK to determine if New Zealand has a relatively high cadmium intake. Interestingly environmental levels (soil and oceanic) in New Zealand were low. Cadmium levels were higher in oysters than in mussels, with New Zealand oysters containing the highest concentration of cadmium presented. New Zealanders also had the highest cadmium burdens in the kidneys and the highest daily intakes. A No Observable Effect Level (NOEL) was calculated from mice data and compared to the daily intakes of the four countries. Both Canada and New Zealand were above this level.
Shellfish are a common mechanism for exposure to both Norovirus and cadmium. The levels of cadmium present in the diet of New Zealanders may be sufficiently high to suppress the immune system, making it more vulnerable to infections of enteric diseases such as Norovirus.
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Contreras, Garces Andrea Maud. "Physiological Effects and Biotransformation of Paralytic Shellfish Toxins in New Zealand Marine Bivalves." Thesis, University of Canterbury. School of Biological Sciences, 2010. http://hdl.handle.net/10092/5181.
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Although there are no authenticated records of human illness due to PSP in New Zealand, nationwide phytoplankton and shellfish toxicity monitoring programmes have revealed that the incidence of PSP contamination and the occurrence of the toxic Alexandrium species are more common than previously realised (Mackenzie et al., 2004). A full understanding of the mechanism of uptake, accumulation and toxin dynamics of bivalves feeding on toxic algae is fundamental for improving future regulations in the shellfish toxicity monitoring program across the country. This thesis examines the effects of toxic dinoflagellates and PSP toxins on the physiology and behaviour of bivalve molluscs. This focus arose because these aspects have not been widely studied before in New Zealand.
The basic hypothesis tested was that bivalve molluscs differ in their ability to metabolise PSP toxins produced by Alexandrium tamarense and are able to transform toxins and may have special mechanisms to avoid toxin uptake. To test this hypothesis, different physiological/behavioural experiments and quantification of PSP toxins in bivalves tissues were carried out on mussels (Perna canaliculus), clams (Paphies donacina and Dosinia anus), scallops (Pecten novaezelandiae) and oysters (Ostrea chilensis) from the South Island of New Zealand.
Measurements of clearance rate were used to test the sensitivity of the bivalves to PSP toxins. Other studies that involved intoxication and detoxification periods were carried out on three species of bivalves (P. canaliculus, P. donacina, P. novaezelandiae), using physiological responses (clearance and excretion rate) and analysis of PSP toxins in the tissues over these periods. Complementary experiments that investigated other responses in bivalves fed with the toxic cells were also carried out. These included byssus production, and the presence of toxic cells in the faeces of mussels, the siphon activity and burrowing depth in clams and the oxygen consumption in scallops.
The most resistant species to PSP toxins were the mussel, Perna canaliculus and the clam, Dosinia anus. Both species fed actively on toxic dinoflagellates and accumulated toxins. The intoxication and detoxication rate of the mussel was faster than the other species of bivalve studied (P. donacina and P. novaezelandiae) which confirm mussels as a good sentinel species for early warning of toxic algal blooms.
The clearance rate of the clam, Paphies donacina decreased when fed on Alexandrium species but the effect of the PSP toxins on this physiological response was not confirmed. Over the detoxification period of 8 days, this clam did not detoxify which suggests that its ability to retain high level of toxins for an extensive period may be critical for public health management.
The scallop, Pecten novaezelandiae was clearly the most sensitive species to the PSP toxins and the clearance rate was significantly lower in the presence of the toxic dinoflagellate A. tamarense. Although the clearance rate was low, the scallops still fed on the toxic dinoflagellate and accumulated PSP toxins in the tissues. The scallops detoxified slowly which would affect the market for this bivalve in the presence of a toxic algal bloom. This bivalve would retain PSP toxins for longer period of time than other species such as mussels.
The oyster, Ostrea chilensis, had erratic clearance rate and did not respond clearly to any of the variables tested over the time. Oysters accumulated more toxins than the sensitive species, but they had been exposed to two more days of feeding with A. tamarense; therefore this species may actually have a similar intoxication responses to P. novaezalandiae and P. donacina.
The results from this thesis suggest further directions for the aquaculture sector and ongoing research in this field, which in future will lead to a better selection of suitable species for culture as well as species for monitoring of PSP toxins. In the future, research that integrates field and controlled laboratory studies will expand to other species of interest and a more complete record will in time be available in order to manage more efficiently the negative effects that harmful algal blooms may have in New Zealand.
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Campos, Carlos Jose Alexandre De. "Contamination of shellfish waters with human noroviruses : environmental risk factors and management options." Thesis, Aberystwyth University, 2016. http://hdl.handle.net/2160/4ccf2977-b58c-456c-8a95-a0f8857b21a7.
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This thesis reports research undertaken to better understand the factors that influence norovirus (NoV) contamination in shellfish production areas (SPAs). This knowledge is necessary to develop control measures for mitigating risk from NoV contamination in SPAs. Predictive models were developed for concentrations of NoV (as measured by the reverse transcription polymerase chain reaction method) and Escherichia coli (as measured by the culture method) in shellfish from 31 harvesting sites and climatic, hydrometric, demographic and pollution source-related characteristics of upstream river catchments. Concentrations of NoV in shellfish increased as water temperature decreased and volume of sewage discharges and river flows increased. Concentrations of E. coli increased as rainfall also increased. Field studies were conducted in an estuary and in a coastal embayment to inform risk management measures for these sites. Concentrations of NoV and E. coli and their removal efficiencies were quantified in effluents from primary, secondary and tertiary treatments at four sewage treatment works. Shellfish were placed at different distances downstream of sewage discharges and tested for NoV and E. coli. Dye tracing and drogue tracking studies were conducted to quantify the dispersion and dilution of sewage effluents. Significant NoV reductions were found as sewage treatment levels increased. Activated sludge was more effective in reducing NoV than trickling filters. Norovirus was frequently detected in sewage effluents and in shellfish. It was found that a NoV limit for shellfish established at 100 copies/g would have a high compliance impact on SPAs. The dispersive characteristics of the dye-tagged effluents were consistent with the variation of NoV contamination in the study sites. A buffer zone established at 1,000:1 dilution of estuarine water to treated effluent would afford a high level of public health protection while a buffer zone established at much lower dilution ratios (e.g. 300:1) would represent a much higher health risk.
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Felice, Renee Jacqueline. "Sensory and Physical Assessment of Microbiologically Safe Culinary Processes for Fish and Shellfish." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/42494.
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Numerous food-borne illnesses are associated with fish and shellfish annually due to consumers choosing to eat seafood raw or undercooked and consumers not properly handling and preparing seafood. The 2009 FDA Food Code suggests intact fish and shellfish should be cooked to an internal temperature of 63°C to target Salmonella spp. Selected fish and shellfish were cooked to 64°C ± 1 and 74°C ± 1 and evaluated for consumer acceptability, characteristics of doneness at temperature endpoints, and physical changes of texture (TPA, KSC, and WB), color, and cook loss. Temperature endpoints represented the recommended internal temperature and ten degrees higher to increase lethality of Salmonella spp. Differences (p < 0.05) in texture were determined among the methods and products tested. However, consumer acceptability (n = 50) for fish and shellfish products (salmon: baked, poached; tilapia: baked, pan-fried; and shrimp: boiled) cooked to 64°C ± 1 and 74°C ± 1 were liked equally (p > 0.05), with mean hedonic scores falling between 6 (like slightly) and 7 (like moderately). A trained descriptive panel (n = 7) reviewed visual and non-oral texture indicators of doneness to distinguish 64°C ± 1 and 74°C ± 1. Firmness and shape of shrimp, separation between muscle flakes and fillet edge color of baked tilapia, and firmness and edge color of the fillet for baked salmon were identified as indicators to determine doneness. Overall, 74°C could be recommended as the internal temperature for cooking fish/shellfish such as salmon, tilapia, and shrimp without diminishing eating quality or acceptability.Master of Science in Life Sciences
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Espourteille, Francois A. "An Assessment of Tributyltin Contamination in Sediments and Shellfish in the Chesapeake Bay." W&M ScholarWorks, 1988. https://scholarworks.wm.edu/etd/1539617592.
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King, Timothy L. (Timothy Lee). "Stock and Species Identification of Selected Marine Fishes and Shellfishes Using Allozyme Analysis and Isoelectric Focusing: Implications for Texas Fisheries Management." Thesis, University of North Texas, 1992. https://digital.library.unt.edu/ark:/67531/metadc277919/.
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Allozyme frequencies and general protein patterns were surveyed among selected Texas marine fishes and shellfishes to illustrate the application of biochemical genetic techniques to stock and species identification in fisheries management.
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Payne, Holly Ann. "DEVELOPMENT OF A METHOD FOR POLIOVIRUS DETECTION IN FRESHWATER CLAMS (COLORADO RIVER, CORBICULA FLUMINEZ)." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275315.
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蕭嘉裕 and Ka Yu Gavin Siu. "An investigation of a toxic red tide dinoflagellate alexandrium catenella: physiology, occurrence andtoxicity." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1995. http://hub.hku.hk/bib/B31235293.
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Cross, Stephen F. "Marine finfish and suspended shellfish aquaculture : water quality interactions and the potential for integrated aquaculture." Thesis, University of Stirling, 2005. http://hdl.handle.net/1893/1861.
Full textAbstract:
The objective of this study was to quantitatively document the culture performance and tissue quality of commercially important deepwater shellfish species (i. e., Pacific oyster, Crassostrea gigas; and Japanese scallop, Patinopecten yessoensis) cultured adjacent to marine finfish aquaculture operations, and to determine (from a production viability and seafood safety perspective) whether integrated finfish-shellfish Multi- Trophic Aquaculture (MTA), or polyculture, is a viable option for the aquaculture industry of temperate regions. Two study sites were employed for this research, one comprising an Atlantic salmon production facility and the other a Pacific salmonf arm. A 2-year assessment program for these sites detailed: (i) oceanographic and physiographicc haracteristics;( ii) organic waste flux, composition and dispersion; (iii) shellfish uptake and contaminant persistence; and (iv) shellfish culture performance. Organic waste flux ranged from 17.11 g/m2/day to 18.35 g/m2/day at the study sites. Phosphorus, calcium, carbon, zinc, cadmium, and strontium were waste constituents that were found at elevated levels at the farm sites with significant declines in concentrations with distance downstream (maximum effect to 100-115 meters). A mass balancee stimation suggested that 85.1% of the organic material (feed) entering the cage was used for fish growth/respiration, 6.8% was lost as settlable solids to the seafloor, and the remaining 8.1% was retained in the water column and a fraction that could affect non-target species (e. g., polyculture candidates) either directly or indirectly. A similar mass balance evaluation for trace metal and chernotherepeutic constituents indicated that 12.9% of the zinc, and an estimated 98.6% of the oxytetracycline contained in feed (during treatment), was released to the water column for potential uptake by co-cultured shellfish. The shellfish monitoring component of this study revealed that trace metal constituents of the feed did become available to the shellfish, although the quantifiable accumulation of trace metals in these non-target species occurred only in close proximity to the cage system and only for the tested scallops (Patinopectin yessoensis). Uptake rates of OTC by shellfish ranged from 0.056 - 0.100 ug/g/day with an associated clearance rate of 0.016 - 0.109 ug/g/day for the respective treatment periods. The comparison of uptake-clearance dynamics suggested asignificant seasonal component to these processes. The physical and biological processes affecting contaminant uptake and clearance rates were identified as important considerations in the management of a proposed integrated-MTA system. A simple Probable Effects Duration (PED) model was developed on the basis of Uptake-Clearance-Persistence plots, illustrating the basis upon which temporal effects of water quality deterioration could be managed in such a system. Shellfish growth was neither impeded nor enhanced as a result of being cultured directly within the influences of a salmon aquaculture facility. An organoleptic test demonstrated that shellfish palatability was not negatively impacted as a consequence of culture proximity to a finfish aquaculture facility. Results of this research suggested that two options are available for developing MTA in coastal temperate waters, i. e., an integrated MTA system and/or an adjacent MTA system. A wide range of MTA social, technical and economic benefits were identified and discussed as a result of this research. It was concluded that the development of a balanced MTA could add measurable environmental benefits to existing aquaculture systemss, setting the stage for future production efficiencies and growth. Given a proper regulatory framework, including seafood (MTA products) and environmental quality surveillanc, the potential water quality impacts on the shellfish component of a finfish-shellfish MTA (identified in this research initiative), and the associated risks over seafood safety, could be effectively managed to support this aquaculture evolution.