Growth and survival of the hatchery larvae of pacific oyster <i>Crassostrea gigas</i> under different concentrations of microalgae and salinity in conditions of southern Primorye

Abstract

Growth and survival rates for larvae of pacific oyster Crassostrea gigas (Thunberg, 1793) hatched in artificial conditions are estimated for the stages of development from D-veliger to pediveliger. The experiment was conducted in the Mariculture Center located on Popov Island (Peter the Great Bay, Japan Sea) for 2 regimes of feeding and water salinity of 26 and 32 ppt. Microalgae Isochrysis galbana, Chaetoceros muelleri and Phaeodactylum tricornutum cultivated in the Mariculture Center were used as a feed in both regimes, in different concentrations. The maximum concentration was 4-fold higher than the minimum one: daily doses of food were 20 and 5 thousand cells/mL for veligers, 40 and 10 thousand cells/mL for early veliconkhes, and 80 and 20 thousand cells/mL for late veliconkhes, respectively, whereas 80 thousand cells/mL for all larvae in transition to pediveliger stage. Statistically significant difference of the growth rate was found for cases with different food concentration (p < 0.05). The larvae with better feeding had higher growth rate under salinity of both 26 and 32 ppt. Besides, the lowered salinity (26 ppt) had some positive effect for growth in the regime of better feeding. Survival rate of the larvae from D-veliger to pediveliger was high under all regimes of the experiment and was estimated for the minimal diet as 77.4 and 64.7 % under salinity of 26 and 32 ppt, respectively, and for the maximum diet as 81.2 and 80.7 % under salinity of 26 and 32 ppt, respectively. According to the experiment results, deficit of food at early stages of the oyster larval development affects negatively on their growth but does not have significant impact on their survival.