Studies on triploid oysters in Australia. I. The farming potential of triploid Sydney rock oysters Saccostrea commercialis (Iredale and Roughley)

A two-and-a-half-year study was conducted to compare the performance of sibling diploid and triploid Sydney rock oysters Saccostrea commercialis (Iredale and Roughley) at three intertidal and one subtidal site in Port Stephens, New South Wales (N.S.W.). The triploid Sydney rock oysters were on average 41% heavier than their diploid siblings after 2.5 years of growth. The triploid oysters also maintained higher dry meat weight and higher condition index (CI) values than their diploid siblings at all sites during the final 10 months' growth to market size (40 to 60 whole weight). The triploid oysters at the subtidal site had the highest CI values recorded in this study. When exposed to the protistan parasite Mikrocytos roughleyi which causes winter mortality disease, no differences in mortality between diploid and triploid groups occurred. These findings have major implications for the N.S.W. oyster industry as triploid Sydney rock oysters can reach market size 6–18 months faster and maintain better meat condition than diploid oysters without an increased risk of winter mortality.