Effects of stocking density on the growth and survival of juvenile silver-lip pearl oysters (Pinctada maxima, Jameson) in suspended and bottom culture

Growth and survival of juvenile silver-lip (or gold-lip) pearl oysters, Pinctada maxima, were compared at two stocking densities (28 individuals per net: 66 oysters per m2 or 48 individuals per net: 99 oysters per m2) with animals held in either suspended or bottom culture. The experiment was terminated during the sixth week because of high mortality in bottom-cultured pearl oysters. Mean (±SE) survival in 28-pocket nets in suspended culture (99.0 ± 1.6%) was significantly better than that in any other treatment (p < 0.01). Survival was also high in the 48-pocket nets in suspended culture (94.8 ± 3.6%). Mean survival in bottom culture was significantly lower (p < 0.05), being 15.8 ± 7.8 and 13.3 ± 3.6%, respectively, for 28 and 48-pocket nets. P. maxima held in suspended culture grew significantly larger (p < 0.001) than those in bottom culture. In both suspended and bottom culture, P. maxima in the 28-pocket nets grew larger (p < 0.001) than those held in 48-pocket nets. Additionally, pearl oysters held in bottom culture had brittle shell margins. These results indicate that culture system had a greater influence on growth and survival than stocking density. Differences in the availability of food are believed to be the major influence on the results obtained; the dry weight of suspended solids, phytoplankton biomass, and phytoplankton diversity were all greater in surface waters