The influence of culture method and culture period on quality of half-pearls ('mabe') from the winged pearl oyster Pteria sterna, Gould, 1851

Abstract

Two groups of 96 winged pearl oysters, Pteria sterna, with mean (± S.D.) dorso-ventral shell height (DVM) of 75.0 ± 6.0 mm, were used to evaluate the effect of two culture methods (pocket nets and plastic cages) on the quality of half-pearls (mabé) produced from them over a period of 9 months. Prior to implantation, oysters were anaesthetized using benzocaine and two plastic nuclei were implanted on the left valve and one on the right valve of each pearl oyster. Oysters were returned to culture conditions and were sampled to determine nacre secretion and pearl quality 5, 7, 9 and 11 months after nucleus implantation. There was no significant difference (P > 0.05) between growth rates of oysters cultured in plastic cages and those held in pocket nets. However, a greater yield of commercial quality pearls was produced by oysters grown in plastic cages. Nacre thickness at the top of the resulting half-pearl blisters showed no significant difference between oysters held in the different culture apparatus (P > 0.05) or between different months (P > 0.05). Highest mabé quality was recorded 9 months after nucleus implantation when water temperatures were low. Growth of pearl oysters during this study resulted in enlargement of adductor muscle, which in some cases grew to cover the mabé. This result indicates that P. sterna with a dorso-ventral shell height greater than 75 mm should be used for the production of mabé. Furthermore, the results suggest that a culture period of 9 months is required to optimize the quality of mabé produced from P. sterna cultured in plastic cages.