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A demographic population simulation model was developed to examine alternative fishery management strategies and their likely effects on the probability of extirpation of local eastern oyster (Crassostrea virginica) populations in the Chesapeake Bay. Management strategies include varying the minimum shell length-at-harvest, harvest rate, and rate and frequency of stocking of oyster seed with respect to varying salinities and oyster population densities. We also examined the rate of disease-mediated mortality that can be tolerated by a viable population. High density populations at low salinity sites remained viable under a 100% harvest rate and 76.6 minimum shell length-at-harvest due to increased fertilization efficiency in high densities, which increased reproduction. Low density populations at low salinity sites remained viable when harvest rate was set at 0.5 and minimum shell length-at-harvest was set at 85 mm. Neither reducing harvest rate nor minimum shell length-at-harvest produced a viable population at high salinity sites. The effects of disease-mediated mortality were too great for these management options to decrease the probability of extirpation to zero. Supplemental stocking conducted regularly reduced extirpation probabilities to zero and pulse stocking (every five to ten years) did as well, although it required a much larger number of oysters to be stocked. Decreasing disease-mediated mortality rates by 20% in high density populations and by 80% in low density populations reduced the probability of extirpation to zero, suggesting the degree of genetic improvement needed to rebuild eastern oyster populations in the Chesapeake Bay. Culture of a non-native species, such as the Suminoe oyster (Crassostrea ariakensis), could supplement harvest of the declining eastern oyster fishery in Chesapeake Bay. Because of possible ecological impacts from introducing a fertile non-native species, introduction of sterile triploid oysters has been proposed. However

A demographic population simulation model was developed to examine alternative fishery management strategies and their likely effects on the probability of extirpation of local eastern oyster (Crassostrea virginica) populations in the Chesapeake Bay. Management strategies include varying the minimum shell length-at-harvest, harvest rate, and rate and frequency of stocking of oyster seed with respect to varying salinities and oyster population densities. We also examined the rate of disease-mediated mortality that can be tolerated by a viable population. High density populations at low salinity sites remained viable under a 100% harvest rate and 76.6 minimum shell length-at-harvest due to increased fertilization efficiency in high densities, which increased reproduction. Low density populations at low salinity sites remained viable when harvest rate was set at 0.5 and minimum shell length-at-harvest was set at 85 mm. Neither reducing harvest rate nor minimum shell length-at-harvest produced a viable population at high salinity sites. The effects of disease-mediated mortality were too great for these management options to decrease the probability of extirpation to zero. Supplemental stocking conducted regularly reduced extirpation probabilities to zero and pulse stocking (every five to ten years) did as well, although it required a much larger number of oysters to be stocked. Decreasing disease-mediated mortality rates by 20% in high density populations and by 80% in low density populations reduced the probability of extirpation to zero, suggesting the degree of genetic improvement needed to rebuild eastern oyster populations in the Chesapeake Bay. Culture of a non-native species, such as the Suminoe oyster (Crassostrea ariakensis), could supplement harvest of the declining eastern oyster fishery in Chesapeake Bay. Because of possible ecological impacts from introducing a fertile non-native species, introduction of sterile triploid oysters has been proposed. However

Considering the economic importance of the Pacific oyster Crassostrea gigas to the French shellfish industry, the appearance of major diseases in this species could cause dramatic decreases in production. Suminoe oysters, of the non-indigenous species Crassostrea rivularis (Gould), were introduced into France to test their ability to adapt to local conditions. These oysters were imported after careful examination, and were maintained in laboratory quarantine. Some mortalities occurred 7 mo after importation. Histological and electron microscope examinations of 9 dead specimens revealed a parasite presumed to be a Bonamia-Like protozoan. This is the first report concerning a parasite of the genus Bonamia in a species belonging to the genus Crassostrea. Thus, C. rivularis is not considered to be a suitable substitute for C, gigas in France.

Considering the economic importance of the Pacific oyster Crassostrea gigas to the French shellfish industry, the appearance of major diseases in this species could cause dramatic decreases in production. Suminoe oysters, of the non-indigenous species Crassostrea rivularis (Gould), were introduced into France to test their ability to adapt to local conditions. These oysters were imported after careful examination, and were maintained in laboratory quarantine. Some mortalities occurred 7 mo after importation. Histological and electron microscope examinations of 9 dead specimens revealed a parasite presumed to be a Bonamia-Like protozoan. This is the first report concerning a parasite of the genus Bonamia in a species belonging to the genus Crassostrea. Thus, C. rivularis is not considered to be a suitable substitute for C, gigas in France.

Considering the economic importance of the Pacific oyster Crassostrea gigas to the French shellfish industry, the appearance of major diseases in this species could cause dramatic decreases in production. Suminoe oysters, of the non-indigenous species Crassostrea rivularis (Gould), were introduced into France to test their ability to adapt to local conditions. These oysters were imported after careful examination, and were maintained in laboratory quarantine. Some mortalities occurred 7 mo after importation. Histological and electron microscope examinations of 9 dead specimens revealed a parasite presumed to be a Bonamia-Like protozoan. This is the first report concerning a parasite of the genus Bonamia in a species belonging to the genus Crassostrea. Thus, C. rivularis is not considered to be a suitable substitute for C, gigas in France.