The primary purpose of this study was to evaluate the feasibility of controlling oyster drills in Tomales Bay, particularly Urosalpinx cinerea and Ocenebra Japonica (astropods, Muricidae), with chemicals which have been succesfully tested on a number of oyster pests, Including urosalpinx, in Long Island Sound (Loosanoff , 1956- 1961). The problem was polo to provide information. en the present status of drills alle is the bay, a basic preliminary in evaluating others of pest control.

The objective of this study was to develop an inexpensive automated device for grading raw oyster meats. The automation technique chosen was digital imaging. Typically, a computer vision system contains a microcomputer and a digital camera. An inexpensive digital camera connected to a personal computer was used to measure the projected area of the oyster meats. Physical characteristics of the oyster meats were important in designing a computer vision grading system and the necessary data were not found in the literature. Selected physical characteristics of oyster meats, including the projected area, weight, height, and volume were measured by independent methods. The digital image areas were found to be highly correlated to oyster meat volumes and weights. Currently oysters are marketed on the basis of volume. The results from this study indicated that the relationship between the oyster meat area as measured by computer vision and volume can be used as a grading criterion. The oysters ranged in volume from 3.5 cm³ to 19.4 cm³ A three dimensional image was not required because the height was not important. Tests showed that the system was consistent and successfully graded 5 oysters per second. The system was calibrated, and the prediction equation was validated with an estimated measurement error of ± 3.04 cm³ at a 95% confidence level. The development of automated graders using digital imaging techniques could help improve the quality and consistency of the graded oyster meats. / Master of Science

The Chesapeake Bay states continue to struggle to achieve the water quality goals set out in the Chesapeake Bay Agreement. While policy efforts to combat eutrophication tend to focus on reducing nutrient loads at point and nonpoint sources, waters of the Bay can be improved through an increase in the assimilative capacity of the ecosystem, which would remove nutrients (called nutrient assimilation services) from ambient waters. The filtering capacity of the native oyster, C.virginica, is a widely recognized means to enhance water quality. With an increase in the number of oysters in the Bay, and no decrease in wild stocks, oyster aquaculture has the potential to also increase the nutrient assimilation capacity of the ambient environment. Yet the expansion of commercial aquaculture in the Bay has been limited by financial constraints. Increased water quality services might be forthcoming if oyster aquaculturists received financial compensation for the nutrient removal services they provide. Based on previous research, this study develops a procedure for estimating annual nutrient removal from a given size oyster aquaculture facility. Next, a firm level bio-economic simulation model was constructed to estimate the amount of compensation needed by a commercial oyster aquaculture firm to make a new investment in oyster aquaculture. The amount of compensation needed is interpreted as the cost of providing nutrient removal by oyster aquaculture. Results indicate that under many circumstances, nutrient removal services can be provided by oyster aquaculture facilities at a per unit cost comparable with some non-point and point source nutrient removal technologies. Finally, a select number of funding resources were identified as potential outlets for creating payments and demand for nutrient assimilation services. / Master of Science

Over the last century the Chesapeake Bay has been plagued by pollution, disease and overharvesting of its resources. As a result, the Bay has been the focus of substantial research and the beneficiary of numerous environmental programs. Previous work has suggested that people are willing to pay for improved water quality in the Chesapeake Bay. For policymakers, the key challenge is to determine how to allocate scarce funds across alternative regulatory and subsidy programs. This thesis investigates three new research questions that relate to the policymaker's problem. First, does WTP for a given water quality improvement depend on the process used to obtain that improvement? Second, does introducing a publicly funded program to improve water quality crowd out private donations to charitable organizations? Third, could oysters in the Chesapeake Bay be successfully marketed as a "green" good? The results from an attribute based choice experiment survey indicate that individuals value process and that they have a higher value for water quality improvement processes that include positive externalities such as increasing oyster populations and planting acres of tall grasses. The results also imply that the new water quality program will crowd out a small portion of private donations to charitable organizations. For example, a $1 tax increase for a new water quality program would crowd out approximately $0.02 of private donations to Chesapeake Bay organizations. Finally, results from a contingent valuation exercise suggest that oyster consumers are willing to pay a significant premium for ecolabeled oysters. Specifically, consumers are willing to pay a 58% premium for half-shell oysters. / Master of Science

The risk of toxin production by Clostridium botulinum type E in pasteurized oysters was evaluated. Thermal death time studies for type E spores in a oyster homogenate showed that the spores survived pasteurization at 550 C; D-values ranged from 65 to 100 min at 700 C and 880 to 1300 min at 550 C. When tubes of oyster homogenate were inoculated with 1x103 type E spores/ml and stored at 3, 6, 12, and 30oC, no growth was observed; however, when the inocculum was increased to 1x104 spores/ml, toxin was produced during storage at 30oC, but not at lower temperatures. For containers of whole oysters inoculated with a low spore level, toxin production occurred during incubation at 6, 12, and 30oC. / Master of Science

Graduation date: 2006

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.

published_or_final_version / Zoology / Master / Master of Philosophy

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.

Thesis submitted in fulfilment of the requirements for the MTech: Oceanography in the Faculty of Applied Sciences at the CAPE PENINSULA UNIVERSITY OF TECHNOLOGY, 2013 / The current status of metal pollution off the South African South coast is not well known. This study was the first to be undertaken in many years using Striostrea margaritacea as a subject species. The aims of the study were to determine the degree of metal contamination in the water, sediments, oyster tissues and oyster shells at sites selected in Witsand, Wilderness and Goukamma, as well as to establish if Striostrea margaritacea qualifies as a successful biomonitor when using lysosomal destabilization as a tool. Seasonal variations between sites were also considered. Other objectives, such as the potential of a Marine Protected Area (MPA) as a control site and the necessity of a monitoring program along the south coast were also included. Sites were sampled seasonally for one year at spring low tides. Ten oysters were collected from each individual site upon each visit. The Neutral Red Retention Time (NRRT) assay was used to determine lysosomal membrane integrity of oyster haemocytes, whereafter oysters were sacrificed for metal analyses. Metals that were analysed are aluminium (Al), copper (Cu), zinc (Zn) and iron (Fe). Metal analyses were done using an Inductively Coupled Plasma - Atomic Emission Spectrometer (ICP- AES). All statistical analyses were performed using ANOVA on Ranks to determine if there were significant differences between sites and between sampling occasions. Aluminium concentrations found in the water column at all sites were considered as low. Iron, zinc and copper concentrations within the water column can on the other hand be considered as high when comparisons are drawn with other studies and data sets. Sediment concentrations for all the metals within the present study were considered to be low when compared to other studies and guidelines. There were not many significant differences recorded between sites and no seasonal patterns were present. Within the tissues of the oysters, the metal ranges are considered to be low when compared to other studies. No definite conclusion about the contamination status of the oyster tissue could be drawn due to the lack of comparative literature. A field study in conjunction with a laboratory experiment should yield more reliable results. There were also no seasonal trends present and very few differences between sites. The bioaccumulation factors were considered as being low with a few exceptions where they were moderate when oyster tissue data was compared to water and sediment data. Concentrations for Al, Zn and Cu in the shells could be considered low when comparisons are drawn, with the exception of Fe that was found to be high. The bioaccumulation factors were considered to be low when oyster shell concentrations were compared to water and sediment data. There were also no seasonal trends present and a prolonged sampling period is suggested to further investigate these findings. When a comparison was drawn between the tissue and shell data a clear pattern was evident. Al and Fe concentrations were highest within the shell where as Zn and Cu concentrations were highest within the tissues of the animal. The theory of mineralization is supported by these findings where bivalves will use their shell as a reservoir for micronutrients and other substances. The NRRT assay revealed that lysosomal membrane destabilization had occurred and that the animals appeared to be stressed for the duration of the sampling period. Site 3, within the MPA, had the longest retention time. The retention times that were recorded were short when compared to other studies. This assay did however show potential as a basic monitoring tool from which more thorough investigations can be initiated. In conclusion, the study sites along the south coast of South Africa does not seem to be contaminated by Al, Zn, Cu or Fe when data is compared to international and local water quality guidelines, sediment quality guidelines and other studies. Also, as concentrations between sites did not differ greatly, it is inconclusive whether or not the MPA can be used as a reliable references site for in situ studies. More vigorous and lengthy studies should be undertaken to contribute to current knowledge of our indigenous species, Striostrea margaritacea and to aid in the development of better management of this resource as well as an ongoing monitoring programme.