The effects of stocking density and ration on survival and growth of winged pearl oyster (Pteria penguin) larvae fed commercially available micro-algae concentrates

Commercially available micro-algae concentrates have been successfully used as an alternative to live micro-algae as a food source during routine larval culture of the winged pearl oyster, Pteria penguin. This supports the development of simplified hatchery facilities and larval rearing protocols that are more appropriate to Pacific island nations. An optimal feeding regime based on these products that also accounts for larval stocking density is yet to be developed. Two experiments were conducted at a commercial pearl oyster hatchery facility in the Kingdom of Tonga to examine the combined effects of stocking density and ration on survival and growth of both D-stage (from 1 to 8 days post-fertilsation) and umbo-stage (from 8 to 17 days) P. penguin larvae. Both experiments used a factorial design combining three larval stocking densities (D-stage: 2, 6 & 10 larvae mL−1; umbo-stage: 1, 3 & 5 larvae mL−1) and three rations (D-stage: 5, 10 & 15 cells mL−1; umbo-stage: 10, 15 & 20 cells mL−1). Survival during D-stage was significantly improved in aquaria stocked below 10 larvae mL−1, whereby a density of 6 mL−1 maximised larval production. An intermediate ration of 10 × 103 cells mL−1 maximised both survival and growth during D-stage. Increasing the initial stocking density of umbo-stage larvae from 1 to 3 mL−1 resulted in significant reductions in both survival and growth. Growth of umbo-stage larvae stocked at a density of 1 mL−1 increased significantly when ration remained below 20 × 103 cells mL−1. The results of this study provide a basis for optimised hatchery culture protocols for P. penguin that are more appropriate to Pacific island nations