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Beaded cultured pearl farming is a lengthy aquaculture process, particularly when the pearl oysters are produced through a hatchery propagation system, and includes the key steps of artificial breeding, larval and spat rearing before graft operations can take place. Within its genus, Pinctada margaritifera has the ability to produce the widest range of pearl colours, thanks to the donor colour polymorphism of the inner shell, which is mainly responsible for colour transmission. As hatchery spat production in P. margaritifera leads to several colour phenotypes (at 3 months old), the aim of this study was to determine whether a relation exists between the colour of the donors as spat and the final pearl colour. In the experiment, which took place over a four-year period, earlier spat colour selection was applied to two hatchery-produced P. margaritifera families. The spat were traced and then used as donors at the adult stage. A total of 1100 experimental grafts were made, using originally grey, green, red and yellow spat phenotypes as donors. The results showed that all spat colour phenotypes mainly produced pearls in the moderately dark (78.4%) and grey colour (56.7%) classes. Differences in darkness level were produced by red and yellow spat, whose pearls were about twice as pale as those from the grey and green phenotypes. Concerning the pearl colour categories, the results showed that the attractive green/blue pearls were obtained twice as often when using grey and green spat phenotypes and that aubergine/peacock pearls were obtained four times more often by using the red and yellow spat phenotypes. This preliminary study suggests that earlier phenotypic colour selection could be applied in P. margaritifera spat as a useful indicator in both pearl production cycles and family selection for donor oyster lines of specific colour propagation.

In French Polynesia, the P. margaritifera pearl aquaculture industry is spread over a vast area, as large as Europe. All the oysters for this the highly economically important activity are supplied from just a few collection lagoons, but they are grown in numerous sites across three archipelagos (Gambier, Society and Tuamotu). Many oyster transfers thus indirectly bring about grafting combinations mixing different geographic origins and production sites. This study aims to examine the impact of such graft combinations on cultured pearl quality traits. For this, six homogeneous and standardised experimental graft combinations (N = 6197) were conducted at commercial scale in the two growing locations the most frequently used in French Polynesia: Arutua atoll (Tuamotu) and Mangareva island (Gambier), using oysters supplied from by the top three collection sites: Ahe, Takapoto and Mangareva lagoons. At harvest, four main pearl quality traits: nacre weight deposition speed, pearl colour components (darkness level and green overtone), grade and shape categories were recorded by a professional sorter from the Tahiti auction and compared. Results revealed effects of the combinations of oyster origin and grow-out location, with: 1) significant origin × site interaction for nacre weight deposition speed; 2) colour variation at intra- and inter-site scales, with Ahe origin producing the most dark pearls and Gambier highest rate of the attractive green coloured pearls; and 3) higher grade categories for the Gambier origin and rearing location. These oyster-site combination effects highlight the benefit for the Polynesian pearl industry of switching from a mono-site/ company production system to a new multi-site production strategy to maximize overall cultured pearl quality expression. Keywords: Pearl oyster, Pinctada margaritifera, Graft combinations, Pearl quality traits, Environment