Emersion Tolerance of Pearl Oyster, Pinctada imbricate Roding, Spat and Juveniles

摘要

Regular air exposure of spat and juvenile pearl oysters, Pinctada imbricata, during culture prompted an evaluation of their tolerance to emersion. Oysters were emersed under conditions chosen to simulate the harshest experienced in Port Stephens, NewSouth Wales, Australia. Temperatures tested were in the range 12 to 36 deg C and fans were used to simulate the desiccative effects of winds. Spat (4.8 mm) and juvenile (12.3 mm) survivals were greatest in the range 16 to 24 deg C. At 20 deg C survival was size dependent, varying between 4 h for 4.8 mm spat to 30 h for 37 mm juveniles. Any additional stress that may be imposed by breaking the byssal attachment of the oysters prior to emersion had no significant effect on survival. In attempts to increase oyster tolerance to emersion, protection against desiccation was of particular importance and significantly increased tolerance. Protection of spat (4.8 mm) from airflow by placing them in plastic bags increased survival times three-fold. Tolerance wasfurther increased if oysters were wrapped in damp paper toweling inside the bags, but the replacement of air with O_2 in bags did not significantly increase survival. With the practical application of these results, oysters (12 to 35 mm) are now routinely emersed and transported for up to 30 h without significant loss.