Method of selecting a suitable site for the growth and survival of the Japanese littleneck clam Ruditapes philippinarum in an artificial nursery ground

Abstract

We examined a suitable site for the growth and survival of juvenile Japanese littleneck clam Ruditapes philippinarum. The survey was conducted in three artiˆcial clam nurseries constructed along the intertidal coastline of Lake Saroma, Hokkaido. Cages accommodating the juveniles were embedded in the oŠshore 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 oŠshore 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 oŠshore side of the nurseries.On the basis of the results, we hypothesized that the oŠshore side of nursery 1 would be suitable for the growth and survival of the juveniles. Around 18,000 juveniles were released in the oŠshore 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.