Progression Of Diseases Caused By The Oyster Parasites, Perkinsus Marinus And Haplosporidium Nelsoni, In Crassostrea Virginica On Constructed Intertidal Reefs

The progression of diseases caused by the oyster parasites Perkinsus marinus and Haplosporidium nelsoni were evaluated by periodic sampling (May 1994-December 1995) of eastern oysters Crassostrea virginica on an artificial reef located in the Piankatank River, Virginia. The infections observed were recorded as a function of: (1) prevalence and intensity; (2) oyster size and age; and (3) depth below mean low water at which the host oyster was found on the reef. Only a very small number of oysters were infected with the two species of pathogens on the oyster reef during the first 11 months of Life. In the second year of oyster life. epizootiological patterns of disease development followed temperature and salinity trends. Oysters at residence depths less than or equal to 45 cm below mean low water exhibited significantly (P \u3c 0.0001) lower prevalence and intensity of infections than oysters at depths greater than or equal to 90 cm. In contrast, oysters at residence depths greater than or equal to 90 cm had significantly higher growth rates (P \u3c 0.05) than those at less than or equal to 45 cm. However, size differences were not significant (P \u3e 0.05) at the end of the study. Results from this study may be used in managing oyster fisheries on natural or artificial reefs