STUDY ON THE QUANTITY OF NATURAL RESOURCES RECOVERY PLAN OF THE SHORT-NECK CLAM BY THE SEVERE ENVIRONMENT EVASION OF THE SUMMER USING The CIRCULATION-TYPE LAND BREEDING DEVICE

We bred juvenile short-neck clams, Ruditapes philippinarum, which collected in June at the tideland of the lower Hiroshima Yahata River, in land breeding device and discharging them again in autumn in order to avoid the summer when the death rate was high because of the large-scale flood and high temperature. We studied to clarify the land breeding condition that had high survival rate of juvenile clams at the same time. The juvenile clams could be bred to have high survival rate by keeping water temperature 15℃, with little difference of growth rate compared to 18℃. In addition, growth rate was improved by a long time feeding of 12 hours. The clams which discharged in the tideland again in October seemed to survive 40-50% by next May, and it was suggested that the clams could contribute to the reproduction of resources.