Zero mortality of P. fucata following mantle excision in this study confirms results for the same procedure undertaken in a preliminary study (Acosta- Salmo´n et al., 2004). There was, however, some mortality of P. margaritifera not immediately following mantle excision but during the mantle regeneration process. Fouling was evident on the inner shell margins of dead P. margaritifera, adjacent to the mantle wound site. This may indicate relatively slow mantle regeneration in P. margaritifera, which allowed fouling organisms to colonise the shells and exert further stress on the oysters. The
P. margaritifera used in this study were older than the P. fucata used. While it is possible that the age of a pearl oyster influences the speed of mantle regeneration, our results may also reflect differences in the rates of mantle regeneration between species of pearl oyster. For cultured pearl production, older pearl oysters are