Suitability of Monospecific and Mixed Microalgal Diets for Spat of the Silver-Lip Pearl Oyster Pinctada maxima

Expansion of pearl production using the silver-lip pearl oyster, Pinctada maxima, depends on increasing the availability of high-quality spat from hatcheries and optimization of existing hatchery protocols. Research to develop feeding regimes yielding higher quality spat is seen as a priority. This study evaluated the suitability of three microalgae (Rebecca salina, Chaetoceros simplex and Tisochrysis lutea), fed singly and in combination, for spat of P. maxima and assessed whether mixed diets yielded spat of higher quality. A model-fitting approach examined the response of spat fed microalgal diets for 35 days. Organic content of spat, as an indicator of quality, as well as metrics relating to spat size and weight were considered. On the basis of organic content, all microalgal diets tested were found suitable and there was no evidence that the mixed diets yielded higher quality spat compared to monospecific diets. Further, any gains in spat size attributed to the mixed microalgal diets were comparatively modest. Contrary to long-held assumptions, our results indicate that monospecific microalgal diets are not necessarily inferior to mixed microalgal diets for on-growing spat of P. maxima. They indicate potential to develop simpler and cheaper protocols for culture of P. maxima spat in land-based systems.