The comparative growth and survival of juvnile tropical oyster (Magallana bilineata, Roding, ۱۷۹۸) using different intensive nursery systems

The bottleneck of the oyster industry worldwide is imposed by the limitation in oyster seed supply and long culture cycles. In developing technology seed production for hatchery seed production to the commercial plant scale, the main challenge lies not only in getting the D- hinged larvae to the settling stage (eyed larvae) but also in growth and survival rates of the juvenile oysters to economically viable levels. Subsequently, efforts are concentrated on research designed at defining optimal conditions for growth and survival of the juvenile oysters cultured using different intensive rearing systems. The nursery systems used in this project are modified and refined technologies used by most hatcheries in the world. Attention is focused on developing oyster seeds or juvenile oysters with good growth and survival rate. Different systems of intensive nursery systems to obtain juveniles with regular shape and size were used. The systems applied in this project were the down-welling system, up-welling system, the rain-down system and the “coke-bottle” system. All these four systems produced cultchless spat, which grew into single oysters. The results of the survival of juveniles (from ۱ week to ۴ weeks) using different nursery systems showed that the best survival and highest growth rate was observed in the up-welling system (۸۹.۳±۷.۳%), followed by the rain-down system (۷۶.۵±۴.۱%) and coke-bottle system (۷۲.۲±۱۲.۰%). The down-welling system showed the lowest survival rate. This may be due to the down-flowing water of the system that made it difficult for the water to flow efficiently in the system, with the juveniles blocking the nitex screen. In general, there are no significant differences in the up-welling system, rain-down system and coke-bottle system for culturing the smaller juveniles. The survival of juveniles (from ۴ weeks to ۲ months) using different nursery systems showed the best survival, and the highest growth was observed in the Coke-bottle system (۹۳.۲ ± ۹.۱%), followed by the up- welling system (۸۵.۶± ۷.۴%). The down-welling system showed the lowest survival rate. The coke-bottle system showed the highest survival rate because of its flow of water moving upwards in a narrower diameter (compared to the up-welling system), which enables the juveniles to be rotated regularly in the system and the food to be distributed evenly in the system.