Effects of Temperature and Salinity on Larval Growth, Survival, and Development of the Sea Cucumber Apostichopus japonicus

For large-scale seed production of sea cucumbers (class Holothuroidea) through a hatchery system, it is imperative to know the effects of environmental variables on larval growth, survival, and development. In this study, separate experiments were conducted to investigate the effects of temperature and salinity on growth, survival, and development of larval sea cucumbers Apostichopus japonicus before feeding (1–3 d postfertilization) and during feeding (5–9 d postfertilization). On day 3, prefeeding larvae showed a maximum survival rate of 95.9% at 21°C and a minimum survival rate of 77.3% at 27°C. On day 8, the highest growth and survival rates of feeding larvae were observed at 21°C (80.7 μm/d and 90.8%, respectively) and 24°C (93.6 μm/d and 87.7%). The highest percentage of doliolaria-stage larvae (34.3%) was observed at 24°C, indicating that the most rapid development of A. japonicus larvae occurred at this temperature. On day 3, the maximum survival rate of prefeeding larvae (92.4%) was observed at a salinity of 30 practical salinity units (psu). On day 9, the maximum growth rate of feeding larvae (65.6 μm/d) and the highest percentage of doliolaria (26.7%) were observed at 30 psu. On day 9, the maximum survival rate of feeding larvae (89.5%) also occurred at 30 psu, whereas no larvae survived at 10, 15, 40, or 45 psu. These results demonstrate that a water temperature of 21–24°C and a salinity of 30 psu are the most suitable conditions for the early development of A. japonicus.