Effects of salinity, stocking density, and algal density on growth and survival of Iwagaki oyster Crassostrea nippona larvae

Abstract

To determine the optimal salinity, stocking density, and algal density for hatchery culture of the Iwagaki oyster Crassostrea nippona larvae, three experiments with salinities of 14, 18, 22, 26, 30, and 34 practical salinity unit (PSU); stocking densities of 0.5, 1, 2, 4, 8, and 12 larvae ml−1; and algal densities of 10, 20, 40, and 100 × 103 cells ml−1 were designed, which included the developmental stages from newly hatched D-larvae to pediveligers. Results showed that larval growth of C. nippona was the fastest at a salinity of 26 PSU, and when salinity was adjusted to a level that was lower or higher than this salinity, survival and growth rate of larvae declined (P 0.05). When feeding the single-algal diet of Isochrysis galbana (clone T-ISO), the shell length of larvae increased markedly as the algal density was increased. Larvae reared at the highest algal density (100 × 103 cells ml−1) had the largest mean shell length; however, under the conditions of our experiment, there was no significant difference (P > 0.05) in growth and survival rates between the treatments at algal densities of 40 × 103 and 100 × 103 cells ml−1. For a large-scale culture, based on the results of this study, a salinity of 26 PSU, stocking density of 0.5–1 larvae ml−1, and algal density of 40 × 103 cells ml−1 are recommended for an early development of C. nippona.