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Walailak J Sci & Tech 2005; 2(2):201-207.

Marine Diatom (Chaetoceros calcitrans) as a Monospecies Diet for Conditioning Oyster (Crassostrea belcheri Sowerby) Broodstock
Piyapong CHOTIPUNTU Schoolof Agricultural Technology, Walailak University, Thasala, Nakhon Si Thammarat 80160, Thailand. ABSTRACT Chaetoceros calcitrans is a marine diatom widely used in aquaculture industries, as it iscomprised of nutritional value suitable for most marine filter feeders. Large amounts of the diatom cells are routinely discharged from shrimp hatcheries as uneaten food. The effluent, rich in algal cells,can potentially be re-used to feed oyster broodstock, as the oysters are an effective filter feeder. This study attempted to investigate viability of C. calcitrans as a monospecies diet forconditioning broodstock of Crassostrea belcheri. It was found that gametes of both sexes developed to spawning condition when rearing in captivity using C. calcitrans. Gametes were found in all four stagesi.e. active, ripe, spawned and spent - at 15.4, 30.8, 30.8 and 23.1%, respectively when reared for 20 days. When the conditioning period was extended for 40 days, the development stages were found at15.4, 15.4, 30.8 and 38.5%, respectively. The whole body weight decreased 2.01-2.65% after 20 days and 7.72% after 40 days. The condition indices were obtained between 6.31-7.78% and showed no relationto gametogenic stages of gonad. This study concluded that C. calcitrans can potentially be used as a monospecies diet for conditioning of oysters C. belcheri broodstock. Key words: Chaetoceroscalcitrans - Crassostrea belcheri Broodstock INTRODUCTION Production of algal food Chaetoceros calcitrans used in marine shrimp hatcheries is labor intensive and costly. Unfortunately large amounts of uneatenalgae are regularly lost from larval rearing systems through water exchange. Effluent rich in algal cells can potentially be re-used in a recirculating oyster-shrimp system as oysters are an...