EFFECTS OF LARVAL SET DENSITY ON SUBSEQUENT GROWTH AND SURVIVAL OF THE SILVER-LIP PEARL OYSTER PINCTADA-MAXIMA (JAMESON)

Pediveligers of the silver-lip (or gold-lip) pearl oyster, Pinctada ma xima, were placed in 15 settlement vessels at densities of 0.5, 1.0, 1 .5, or 2.0 larvae/mL 16 days after fertilization. The number of settle d spat per 100 cm(2) was estimated on Day 23 and again on Day 44. The number of spat/100 cm(2) in the 1.0 larva/mL treatment was over double , and significantly greater (p < 0.05) than that in the 0.5 larva/mL t reatment. Increases in the number of spat per 100 cm(2) were not signi ficant (p > 0.05) between larval densities of 1.0 and 1.5 larvae/mL an d 1.5 and 2.0 larvae/mL. Highest mean survival was observed in the 0.5 larva/mL treatment; however, this was not significantly greater (p > 0.05) than that in other treatments. By day 44, spat from the 0.5 larv a/mL treatment had a mean antero-posterior shell length (SL) of 1.87 /- 0.08 mm and were significantly larger (p < 0.05) than spat in all o ther treatments. Spat in the 1.0 larva/mL treatment were significantly larger (p < 0.05) than those in the 1.5 or 2.0 larvae/mL treatments. Differences in Si between the 1.5 and 2.0 larva/mL treatments were not significantly different. Differences in size were most likely attribu table to competition for space and food. Based on the results of this study, a setting density of no more than 1.0 larva/mL is recommended f or P, maxima. To maximize survival and growth of P. maxima spat, a den sity approximating 70 spat/100 cm(2) is recommended.