1Mie Prefecture Fisheries Research Institute, Shima, Mie 517-0404, 2Graduate School of Bioresources, Mie University, Tsu, Mie 514-8507, Japan
The relationship between the duration of post-operative holding in low salinity water (25 psu) and the yield of high-quality pearls was examined. Implanted oysters were immersed in low salinity seawater (low salinity treatment: LST) for 1, 4, 8, or 14 d. After treatment, the oysters were suspended from a raft in Ago Bay. The control group consisted of oysters that did not receive the LST after implantation of the nuclei. The oysters were cultured in Ago Bay for several months. Harvested pearls were classified as nacreous, or others (prismatic, organic, nucleus). Moreover, nacreous pearls were examined for deformations and blemishes on the surface and their diameter was measured with a digital vernier caliper. The proportion of high-quality pearls tended to be positively correlated with the duration of LST up to a maximum of 8 d after nucleus implantation. However, the proportion of high-quality pearls was lower in oysters subjected to 14 d LST than 8 d LST. The diameter of round nacreous pearls was significantly lower in oysters subjected to 14 d LST than 8 d LST or in the control. Our results suggest that 8 d LST is optimal for the production of high-quality pearls.