Effects of stocking density on growth and survival of early juvenile silver-lip pearl oysters, Pinctada maxima (Jameson), held in suspended nursery culture

Abstract

This study investigated the effects of stocking density on the growth and survival of juvenile silver-lip (or gold-lip) pearl oysters, Pinctada maxima. Spat were resettled onto PVC slats (75 × 500 mm 2) and held in suspended nursery culture for 6 weeks at four stocking densities: ten juveniles per slat (1.3 juveniles per 100 cm 2); 50 juveniles per slat (6.7 juveniles per 100 cm 2); 100 juveniles per slat (13.3 juveniles per 100 cm 2) and 150 juveniles per slat (20 juveniles per 100 cm 2). Best survival was recorded at a stocking density of ten juveniles per slat (80 ± 4.36%, mean ± s.e.) which was significantly higher than the other densities tested ( P < 0.05). Survival did not differ significantly between the other densities tested ( P > 0.05). Best growth, measured as wet weight, shell length and shell height, was shown at a density of ten juveniles per slat, where wet weight and shell length were significantly greater than at any other stocking density ( P < 0.05). Shell height was also significantly greater at a density of ten juveniles per slat than at all other stocking densities with the exception of 50 juveniles per slat. Spat were significantly ( P < 0.05) smaller at each increase in stocking density from 50 juveniles per slat to 150 per slat. The incidence of growth deformities increased with increasing stocking density. These increases were significant ( P < 0.05) between all densities apart from 100 juveniles per slat and 150 per slat, where the difference in the number of deformed animals was not significant ( P > 0.05). The ratio of shell height to shell length was also influenced by stocking density. Differences between the shell height:shell length ratios were significant between all stocking densities ( P < 0.05) except 100 juveniles per slat and 150 juveniles per slat, where there were no significant differences ( P > 0.05).