Recruitment of the Eastern Oyster in Coastal Georgia: Patterns and Recommendations

Abstract

The recruitment levels of the eastern oyster Crassostrea virginica were monitored during 1991–1994 to investigate the feasibility of collecting natural spat for conservation or maricultural purposes in coastal Georgia. Recruitment levels were measured on three temporal (biweekly, monthly, and seasonally) and three spatial scales (subtidally, at mean low water, and intertidally), at three sites (House Creek, Skidaway River, and Priest Landing) from April through November in each year. Recruitment generally commenced in May and continued through October, usually peaking in August. Recruitment was highest at the House Creek site and varied greatly among the sites. Distinct differences in recruitment patterns occurred among the temporal scales sampled. For the biweekly collectors, recruitment was highest on the subtidal collectors. On the monthly collectors, low-water and subtidal returns tended to be similar and were higher than the intertidal returns. For the seasonal collectors, intertidal collectors had significantly greater spat numbers. Monthly collections yielded an average of 6,100 eastern oyster spat/m2 on all tidal heights combined; whereas, seasonal sampling yielded means up to 7,000 spat/m2 on intertidal collectors alone. Recruitment of the eastern oyster in coastal Georgia can be extremely high, but can also show a large degree of spatial and temporal variability. Smaller, sheltered tidal creeks throughout the marshes are more reliable sources of wild spat than the larger more open bodies of water. The high degree of variability within the biweekly collecting regimes makes prediction of recruitment on a biweekly basis extremely difficult. Consequently, collection of spat for management or mariculture purposes should be based on the more consistent monthly and seasonal sampling regimes.