Effects of Salinity and Temperature on Growth and Survival of Juvenile Iwagaki Oyster Crassostrea nippona

Iwagaki oyster Crassostrea nippona occurs naturally along the coasts of Japan and Korea. Because of its unique flavor, delicious taste, edibility during the summer and high commercial value, it has been identified as a potential aquaculture species. To determine the optimum aquaculture conditions and provide necessary information for mass production of the juvenile, the effects of six salinities (15, 20, 25, 30, 35 and 40) and five temperatures (16, 20, 24, 28 and 32A degrees C) on growth and survival of juvenile C. nippona were examined in this study. In the salinity experiment, the largest values of mean shell height and growth rate were observed at salinity 25 (20.96 +/- 0.36 mm and 172.0 mu m d-1, respectively), which were significantly different (P < 0.05) with those of other treatments, except at salinity 30 (20.56 +/- 1.05 mm and 160.3 mu m d(-1), respectively) (P > 0.05). The maximum survival rate 84.44% was always observed at salinity 20, and there was no significant difference (P > 0.05) in survival rate among salinities varying between 15 and 35. In the temperature-related experiments, the highest growth and survival rates of juvenile were observed at 24A degrees C (180.8 mu m d(-1) and 84.4%) and 28A degrees C (190.7 mu m d(-1) and 83.3%), respectively, on day 20, and showed significantly (P < 0.05) larger size and higher survival rate than any other groups. Both juvenile survival and growth were significantly depressed at extreme salinities (15, 40) and temperatures (16A degrees C, 32A degrees C). Based on the results of the present study, a salinity range from 25 to 30 and a temperature range from 24A degrees C to 28A degrees C are considered optimal conditions for survival and growth of juvenile C. nippona.