The effects of tidal and bottom placement on the growth, survival and fouling of the eastern oyster Crassostrea virginica

Oysters Crassostrea virginica in Georgia are naturally small and grow in cl usters; however, it is more profitable to harvest large, single oysters. Th is study attempts to identify favorable tidal and bottom placements for the grow-out of large, single oysters in Georgia. Three bags, each containing 50 single oysters, were placed in four different tidal positions (subtidal on-bottom, subtidal off-bottom, intertidal on-bottom and intertidal off-bot tom) at five sites in House Creek, Georgia. Measurements of oyster growth, survival and degree of oyster spat fouling were taken seasonally (every 3 m o). Oysters from on-bottom treatments exhibited significantly lower growth (P = 0.0364 intertidal only), survival (P = 0.0044) and degree of fouling ( P = 0.0154) than oysters from the intertidal off-bottom treatment. However, the oysters placed intertidally off-bottom were heavily fouled during the recruitment period. It may be necessary to sacrifice some growth and surviv al by culturing oysters intertidally on-bottom during the recruitment perio d in order to reduce the degree of fouling. During the non-recruitment peri od, placing oyster culture bags intertidally off-bottom maximizes growth an d survival.