The settlement of hatchery produced spat of the blacklip pearl oyster Pinctada margaritifera was investigated with respect to time of introduction of settlers, type of cultch material and the larval (pediveliger) densities. The study clearly indicated that the ideal time for deployment of spat collectors in the hatchery is when the pediveligers are beginning to appear in the larval
rearing tank. In similar larval stocking densities, the settlement was more on the spat collectors which were deployed when the larvae had not metamorphosed to spat. Six different types of cultch materials were tested for their efficiency in three larval densities. The study showed that better spat collection of P. margaritifera can be achieved in hatcheries by providing
darkness, and employing dark coloured, rough-surfaced, corrugated and conditioned spat collectors such as the garden shade spiral at higher larval densities of 1.0 nos/ml.

Pinctada margaritifera, hatchery, larval stocking density, collectors, spat settlement.