Nacre growth and thickness of Akoya pearls from Japanese and Hybrid Pinctada fucata in response to the aquaculture temperature condition in Ago Bay, Japan

Abstract

This study examines whole nacre thickness and monthly growth of pearls of Akoya pearl oyster, Pinctada fucata, which came from Japanese and hybrid strains and relate them to the water temperature of the aquaculture site in Ago Bay. Whole nacre thickness of the pearls was significantly different between Japanese and Hybrid strains (Student's t-test, p-value <0.01), pearls of Japanese strain tend to be thicker than those of Hybrids. This is due to different nacre growth rate between the two strains especially in summer, Japanese strain grew faster than Hybrid in August until November (Student's t-test, p-value <0.01), even though there was no significant difference in December when both strains showed very slow growth of pearl nacre due to the low water temperature. Monthly nacre tablet thickness of pearls of Japanese strain was thicker than that of Hybrid in August, September and November (Student's t-test, p-value <0.01) but no significant difference in November and December. The result of this study shows that pearl nacre growth and thickness are related to the water temperature of the aquaculture site. The fact that both oysters have different range of optimum temperature to grow leads to the possibility of different quality of pearls from both strains since whole nacre thickness, nacre growth and nacre tablet thickness can determine the quality of pearls. Statement of relevanceThe findings of this study will redound to the benefit of commercial aquaculture of pearl oyster in the world generally, and in Japan especially considering that cultured pearl is one of the important aquaculture products in Japan and some other Countries.