ASSESSING PROTECTIVE CYLINDERS FOR CHAPLET-BASED CULTURE OF THE WINGED PEARL OYSTER PTERIA PENGUIN

This study assessed the use of novel, locally made, protective culture cylinders as a means of improving pearl oyster Pieria penguin performance and standardizing culture methods used by mabe pearl farmers in Tonga. Cylinders were constructed from locally sourced wire mesh, for a cost of USD 12.1 each and were used to protect oysters grown on chaplets. Growth and survival of two age cohorts of oysters-young (0.7-y-old and 33.1 +/- 0.7-mm dorsoventral height (DVH)) and old (2.7-y-old and 86.9 = 0.8 mm DVH)-cultured using this system were determined every 3-5 wk over an 11-mo period. The DVH of young oysters increased by 74.6 mm, wet weight (WW) by 161.2 g, and shell thickness (ST) by 23.4 mm, whereas for old oysters, DVH, WW, and ST increased by 55.2 mm. 271.4 g, and 14.7 mm, respectively, over the same period. Young oysters held in culture cylinders reached the starting size of the old oyster cohort within seven months of growth and at less than half their age (1.2 and 2.7 y old, respectively). Young oysters held in culture cylinders also showed a 3-fold greater monthly growth rate than oysters cultured in trays (6.8 and 2.1 mm month(-1), respectively). Survival of oysters in culture cylinders over the 11-mo culture period was 91.7% and 97.6% for young and old oysters, respectively, compared with 25% for oysters cultured in trays. The use of protective cylinders for P. penguin culture increases oyster survival and reduces the culture period required for P. penguin to reach minimum pearl production size by >50% relative to the current tray-based culture method, supporting improved mabe pearl farm profitability.