Abstract
Size is the most important and valuable quality trait of cultured pearls produced by the black-lipped pearl oyster, Pinctada margaritifera. In French Polynesia, several breeding programmes have been started that aim to improve this size trait, which is highly related to shell growth rate in both recipient and donor oysters. Shell growth rate dictates the time of grafting, size of implanted nuclei and bio-mineralisation potential of the mantle and pearl sac. We assessed shell growth rate through routine digital shell biometric analysis on 22 hatchery families produced between 2005 and 2008. These included full-sib families and half-sib families derived from polyandry (one dam crossed with two or more sires). Results showed that: 1) a significant family effect was recorded for growth performance, analysed according to the Von Bertalanffy model, 2) a significant male effect was observed for some of the half-sib families and 3) a relationship was found between the shell growth performances of five families randomly selected and used as graft donors in a grafting experiment and the final weight of the cultured pearls produced. These results have important implications for the breeding of pearl oysters with high growth capacities: it may be possible to select oyster lines for the potential to produce large pearls using shell equivalent diameter estimated by the digital method as a selection criterion.
Highlights
The black-lip pearl oyster Pinctada margaritifera is a widespread species, occurring across the Indian and Pacific Oceans and in the eastern Mediterranean Sea
Our study demonstrates that the potential exists to improve pearl growth rates in P. margaritifera
To improve cultured pearl size via selection, a multi-trait approach should be used, integrating several oyster lines, considering the key role played by recipients, and taking into account quantitative genetic control, environmental effects and associated correlations
Summary
The black-lip pearl oyster Pinctada margaritifera is a widespread species, occurring across the Indian and Pacific Oceans and in the eastern Mediterranean Sea. By 2013, this industry had developed on 25 islands and atolls, with 517 pearl farms located across three archipelagos: Tuamotu (398 farms), Gambier (79 farms), and Society (40 farms) [4]. This industry has been declining since 2001 and is facing a critical situation due to a combination of several economic factors: slowdown of the world economy, overproduction of pearls, and poor average pearl quality. It is estimated that only 5% of harvested pearls can be classed as grade A quality according to local regulatory standards [5]. There is a need to take measures that will enhance pearl quality, increasing the proportion of high value pearls
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