REMAINING EFFECTS OF ASARI CLAMS Ruditapes philippinarum ON SPREADED CRUSHED STONES SUBJECT TO OSCILLATORY FLOW

Abstract

 The Asari clam Ruditapes philippinarum is one of the important fishery species in Japan, but its re-source has been decreasing since mid-1980s. As one of the reasons, it has been assumed that Asari clams cannot remain on the sea bottom due to strong wave. Previous studies indicated that Asari juveniles had better growth and survival rates on fishery ground by spreading crushed stones than on natural fishery ground in Chiba and Mie Prefectures. However, we have not clarified the mechanisms to enhance the remaining rate of Asari clams by crushed stones. In this study, as an aim at verifying effects of Asari fishery ground by spreading crushed stones, we calculated the remaining rate of Asari clams on crushed stones to various wave strength based on constructing a theological formula and conducting laboratory experiments using the circulating water channel (about 12 m in length, about 0.5 m in width, about 0.5 m in depth) owned by National Research Institute of Fisheries Engineering, Japan Fisheries Research and Education Agency. Consequently, we found that Asari juveniles were easy to stay on larger size of crushed stones under the strong waves whatever water temperature. In the future, the theological formula is expected to be a guide for development of Asari fishery ground.