1School of Biological Science, Tokai University, Sapporo, Hokkaido 005-8601, 2Hokkaido Government Kushiro General subprefectural Bureau, Kushiro, Hokkaido 085-8588, 3Hokkaido Research Organization Central Fisheries Institute, Yoichi, Hokkaido 046-8555, 4Lake Saroma Fisheries and Aquaculture Co-operation Organization, Kitami, Hokkaido 093-0216, 5Nishimura Gumi Co., Ltd., Yubetsu, Hokkaido 099-6404, 6Tokyo Kyuei Co., Ltd., Kawaguchi, Saitama 333-0866, 7National Research Institute of Fisheries Engineering, Kamisu, Ibaraki 314-0408, Japan
We examined a suitable site for the growth and survival of juvenile Japanese littleneck clam Ruditapes philippinarum. The survey was conducted in three artificial clam nurseries constructed along the intertidal coastline of Lake Saroma, Hokkaido. Cages accommodating the juveniles were embedded in the offshore side of nurseries 1, 2, and 4 in April; then, juvenile growth was investigated after 6 months. The proportion of the juveniles that would be dislodged from the sand by bottom disturbance due to wave action was calculated using a simulation model. Caging experiments revealed that the offshore side of nursery 1 was suitable for achieving high shell growth. The simulation suggested that the survival rate of the juveniles was higher towards the offshore side of the nurseries. On the basis of the results, we hypothesized that the offshore side of nursery 1 would be suitable for the growth and survival of the juveniles. Around 18,000 juveniles were released in the offshore and land sides of nurseries 1 and 4. Mean shell length and survival rate of the juveniles in nursery 1 was 1.7 and 4.4 times as high as that in nursery 4 after 12 months of releasing; this result supported our hypothesis.