Culture of Juvenile Atlantic Surfclams, Spisula solidissima solidissima and Spisula solidissima similis, in Forced-Flow Upwellers in a Bivalve Hatchery in Coastal Georgia

Four experimental growth studies for juvenile Atlantic surfclams, Spisula solidissima solidissima and Spisula solidissima similis , under hatchery conditions were conducted in 10-cm diameter forced-flow upweller units. Experiments were designed to determine optimum food ration (2%, 5%, and 8% g dry weight of algae/g wet weight of clam), water culture temperature (20, 25, and 30°C), flow rate (2, 4, and 6 Lpm), and stocking density (7, 14, and 21 g wet weight of clams) for rearing juvenile clams in upweller units. Each experimental trial was performed for a 14-d period. Nested Analysis of Variance showed that juvenile surfclams Spisula solidissima similis grew significantly faster at a temperature of 20°C and food rations of 5 % and 8%. In all four experiments, clam mortalities were not observed except in the temperature experiment, where total mortality occurred for clams cultured at 30°C. Clam growth in biomass and size decreased significantly with increases in culture temperature. For Spisula solidissima solidissima , clam growth was significantly reduced in terms of size and biomass at a flow rate of 6 Lpm. No difference in size or biomass was determined between clams grown at a flow rate of 2 or 4 Lpm. Surfclams at the lowest stocking density of 7 g wet weight significantly increased more in net biomass compared to those at higher stocking densities. Clams were significantly larger in shell length when grown at the two lower stocking densities compared to those at the highest stocking density. Hatchery-rearing protocol for juvenile surfclams is discussed.