Growth and mortality of Ostrea edulis at two sites on the Damariscotta River estuary, Maine, USA

The Damariscotta River estuary is a center of oyster culture in Maine, yet the comparative performance of flat oysters Ostrea edulis at different loca tions in this now Bonamia ostreae-enzootic estuary has not been assessed. J uvenile O. edulis were deployed in July 1997 among replicate floating trays at one estuarine (Little Point) and one marine site (Lowes Cove), and grow th, mortality, and B. ostreae prevalence were compared through December 199 9. Growth was faster at Little Point though oysters at both locations reach ed market size in less than three full growing seasons. Mortality was simil ar between locations except following a June 1998 rain event that decreased salinity more precipitously at Little Point. Cumulative mortality was grea ter at Little Point (45.8%) than Lowes Cove (26.7%). Surprisingly, B. ostre ae was observed in only a single oyster from Little Point in May 1998. Thes e data indicate that flat oysters in Maine may grow well across a wide rang e of environments, yet may demonstrate better survival at marine sites wher e salinity fluctuations are less extreme. While B. ostreae is likely still a threat, selection of sites where rapid growth to market size is possible may reduce its impact.