Larval and spat culture of the Western Australian silver- or goldlip pearl oyster, Pinctada maxima Jameson (Mollusca: Pteriidae)

Abstract

The larvae of Pinctada maxima were fed Tahitian Isochrysis galbana, Chaetoceros calcitrans, C. gracilis and Nannochloropsis oculata. Food concentrations for larvae were increased gradually from 0.2–2 algal cells·μl −1 on day 1 to 20–40 cells·μl −1 on day 30. Initial stocking densities of 1–8 larvae·ml −1 were reduced to 0.5–1 larvae·ml −1 at settlement. For 70% of the population, settlement began on day 24 and lasted up to 7 days. Ten to 15% of the population failed to grow appreciably and another 10–15% grew comparatively rapidly, reaching settlement by days 15–17. The smallest spat observed on day 28 was 331 μm shell length (SL)×305 μm shell height (SH). Spat were fed the same phytoplankton as the larvae, as well as Tetraselmis chuii twice daily at 40–285 cells μl −1 over 5 months. Spat reared in downwellers at densities of 4 and 25 individuals·100 cm −2 grew 9.6 and 6 mm·mth −1 SH, respectively. Those reared in plastic cages at sea at densities of 3 and 7 individuals·100 cm −2 grew 9.2 and 7.3 mm mth −1 SH, respectively. Mortality 5 months after settlement was 1–2% for those reared in the hatchery and 9–12% for those reared at sea. Hatchery-propagated spat were similar in appearance to natural spat and 20–25% were suitable for pearl culture 19 months after fertilization, or when they were 120 mm SH.