Effects of different substrates on settlement and growth of pearl oyster (Pinctada maxima) larvae in hatcheries

Metamorphosis of pearl oyster Pinctada maxima pediveliger is affected by physical and chemical characteristics of the collectors. In the present study, we conducted four experiments to evaluate the effects of collector characteristics on the settlement and growth of hatchery-reared pearl oyster. In the first experiment, black, red, yellow, and white plastic sheets were used as collectors. Settlement of P. maxima larvae in black and red plastic sheets was significantly higher than that in yellow and white plastic sheets (P < 0.05). Mean shell length was not significantly different among the four colored sheets (P > 0.05). In the second experiment, pediveliger larvae were settled onto palm rope and polypropylene rope collectors. The number of spat in the palm rope collector was significantly higher than that of spat in the polypropylene rope collector (P < 0.05). Mean shell length was not significantly different between palm rope and polypropylene rope collectors (P > 0.05). In the third experiment, settlement and subsequent growth were compared between plastic sheets with and without biofilm. The number of spat in the plastic sheets with biofilm was significantly higher than that in the plastic sheets without biofilm (P < 0.05). Mean shell length after settlement were not significantly affected (P > 0.05). In the fourth experiment, pediveliger larvae were stored in tanks with (experimental group) and without collectors (control group). The settlement rate of larvae on the wall was not significantly different between the two groups(P > 0.05). The settlement rates of the larvae on the wall and collectors in the experimental group were significantly larger than those on the wall in the control group(P < 0.05). Mean shell length was not significantly different between the groups (P > 0.05). Our results suggest that appropriate selection of collector types, color, and conditioning can improve the settlement of P. maxima larvae in hatcheries.