1995 Volume 61 Issue 5 Pages 739-742
To elucidate the influences of food deprivation on the mortality of the pearl oyster Pinctada fucata martensii, the pearl oysters were held unfed at an environmental seawater temperature of 23-29°C from early June to late September in 1985 (115 days). The mortality of unfed pearl oysters increased from day 70 of unfed cultivation. Cumulative mortalities reached 95% on day 115 from the start of unfed cultivation. During the unfed period, the glycogen content of adductor muscle decreased rapidly during the first week. Dry meat weight losses increased more than 70% and condition index decreased from 13.7 (initial) to 4.0 on day 70 of unfed cultivation. Crystalline style weight also decreased continuously as well as dry meat weight and condition index. On the other hand, wet meat moisture content increased from 81 to 91%.
It is thought that unfed pearl oysters can not survive when they waste their nutritive reserves and there may be a critical survival limit of pearl oysters under the unfed condition. In this study, when the condition index dropped below 4 and dry meat loss increased more than 70%, the mortality of unfed pearl oysters remarkably increased. These values may be valid indicators for the critical survival limits of pearl oysters under the unfed condition.