EFFECT OF TIMING OF SEED DEPLOYMENT ON GROWTH AND MORTALITY OF OYSTERS, CRASSOSTREA-VIRGINICA, AFFECTED BY JUVENILE OYSTER DISEASE (JOD)

Mortality of oysters, Crassostrea virginica, caused by Juvenile Oyster Disease (JOD) has been a chronic problem the northeastern United Stat es since 1988. To assist in identifying potential health management op tions, the effect of time of spawning and deployment of oysters on res ultant growth and mortality was examined in the Damariscotta River, Ma ine. Broodstock oysters from a line selected for fast growth were spaw ned at 2-wk intervals between 28 March and 19 July 1995. Duplicate gro ups of juvenile oysters from each spawn were deployed in floating tray s between 23 May and 31 August. Mortality and size of all cohorts were determined from late June to early December. Cumulative mortality of oysters was related to the timing of deployment. Cohorts placed in the river before June or after mid-August had cumulative mortalities of 2 0% or less. Oysters deployed between 8 June and 18 August had cumulati ve mortalities ranging from 64-96%. Growth of all cohorts was rapid im mediately after deployment but decreased once JOD began to have an eff ect. Final size of oysters was directly related to age. This study det ermined that seed oysters placed in the Damariscotta River between Jun e and mid-August will experience high mortality and low growth. Potent ial management options to reduce JOD impact include 1) early spawning and deployment in May, ensuring that a mean shell height >25 mm is rea ched prior to August and 2) late spawning and deployment after mid-Aug ust to avoid exposure to JOD.