Performance of the winged pearl oyster Pteria sterna (GOULD, 1851), implanted for half-pearl (mabé) production in two size groups

This study generated baseline information relative to overall performance of the winged pearl oyster Pteria sterna implanted at two groups (small and large) for half-pearl (mabé) production. This is a suitable technology to optimize the pearl production in the tropical coasts of Ecuador. The yield and quality of mabé pearl produced, as well as oyster condition index, increase in oyster survival, shell size and mass of tissues, and environmental variables were examined in this study. From 120 oysters used, 65 were of small size (25 nucleated, 25 non-nucleated and 15 for the initial sample; initial average shell length of 64.7 ± 5.3 mm; ~6 months old) and 55 were of large size (20 nucleated, 20 non-nucleated and 15 for the initial sample; 78.0 ± 5.8 shell length cm; ~10 months old). Hemispherical plastic nuclei (12.5 mm base diameter, 7 mm height) were used. All groups of oysters were anesthetized with 1% Eugenol and cultivated for five months (May through October 2017). At the end of the trials, only one dead oyster occurred in the small size group. A high percentage (29.2%) of adductor muscle over-growth on the nuclei occurred in small oysters, probably caused by the relatively fast growth rate (≥8 mm in 5 months). A lower percentage of muscle over-growth on the nuclei (5.6%), thicker nacre deposition, and higher occurrence of regular-shaped mabé pearls were observed in large oysters, compared to small oysters. This study suggests that large oysters (>80 mm) should be preferably used for half-pearl production in P. sterna to ensure the highest quality standards for commercialization. •Mabé production was more successful in large oysters (100%) than in small oysters (92%).•Muscle overlap on the nuclei occurred more often in small (29.2%) than in large oysters (5.6%).•Thicker nacre layers in large (1.2 mm) and small oysters (0.56 mm) occurred in just four months.•Lower increments in shell size were observed in small and large oysters implanted with nucleus.