Nursing and Grow-Out of Hatchery-Reared Big Oyster (Crassostrea belcheri Sowerby 1871) in the Intertidal Mangrove Area

Abstract

The nursing of hatchery-reared juvenile oysters (Crassostrea belcheri Sowerby 1871) in the intertidal mangrove area was carried out over four months. The initial average width and length of the seed were both 2±0.05 mm, while average seed weight was 0.29±0.05 g. At the end of the experiment, the oyster seed reached 3.38±0.39 and 3.54±0.89 cm for average width and length, respectively and weighed an average of 3.22±2.01 g. The mean increase in daily growth rate of the shell width and length ranged from 0.13 to 0.29 and 0.12 to 0.38 mm/individual, respectively. The mean increase in live weight ranged from 0.16-0.39 g/individual. The mean survival rate was 22.52% at the end of the nursing experiment. For the grow-out experiment, oysters from the nursing experiment which were five cm or bigger were chosen and placed in flipping pouches in the intertidal zone for six months. At the end of this grow-out experiment, the mean increases in shell width and length were not significantly different among the treatments (p>0.05). However, there were significant differences in survival and in the amount of barnacle attachment among the treatments (p<0.05). A high survival rate was found with all densities after a five hour exposure to air at low tide during the spring tide period. The highest number of attached barnacles was found after an exposure to air of one hr at the lowest tide during spring tide.