It is widely assumed that pearl oysters, Pinctada margaritifera, producing low quality pearls with concentric
grooves or ‘circles’ are unlikely to produce pearls with improved quality if grafted again for pearl production.
Such oysters are often discarded. However, if these oysters are capable of improved pearl quality when regrafted,
this would provide opportunities for improved income for pearl farmers. This study aimed to determine
whether oysters producing circled pearls are able to produce pearls with improved quality after re-grafting. A
total of 100 oysters that produced circled pearls and would have normally been discarded were re-grafted and
the quality of successive pearls produced by individual oysters was compared in terms of shape, size, lustre, colour,
surface perfection and overall quality. The proportion of pearls with circles decreased from100% of first graft
pearls to 48% after the second graft, and 18% of second graft pearlswere classified as ‘semi-round’ and superior in
shape to all first graft pearls. There was a significant improvement (p=0.04) in the overall shape of second graft
pearls compared to first graft pearls. The highest proportion of pearls (63%) fromthe first graftwere 10–11mmin
size while the majority of second graft pearls (51%) were 11–12mmin size, and the differences in pearl size between
first and second graft were significant (p = 0.04). Second graft pearls had poorer lustre than first graft
pearls with a higher proportion of dull pearls, a lower proportion of medium lustre pearls and no pearls with
high lustre. Despite this, the number of pearls in different lustre categories after the first and second graft did
not differ significantly (p = 0.07). For overall grading, most first graft pearls (83%) were assessed as ‘C’ grade
with 17% categorised as ‘D’ grade. Similarly, most second graft pearls (78%) were assessed as ‘C’ grade and 20%
as ‘D’ grade; however, 2% of pearls were assessed as ‘B’ grade which were not present in first graft pearls. Nonetheless,
the number of pearls belonging to different gradeswas not significant (p=0.08). Our data show for the
first time that that production of circled pearls after second graft is not obligatory for P. margaritifera that produced
circled pearls after first graft. They further show that marketable pearls can be produced from oysters
that are normally discarded after the first pearl harvest and this has potential to generate increased revenue.