This study examined the effects of oscillatory water flow, with reference to flow speed and amplitude period, on the burrowing behaviors of the Japanese surf clam Pseudocardium sachalinensis (shell length=5.7-41.7mm) using a vertical water-circulating tunnel. The burrowing speed of the clam tended to rise with the shell length and flow speed regardless of amplitude period and the clam's posture at burrowing toward flow. The relationship between the burrowing speed (V: mm/s), shell length (L: mm) and flow speed (U: cm/s) was described as V/L=4.66×10-4U+0.015. A large number of the clams apparently burrowed in a lateral direction toward the flow. The maximum flow speed when the clams could burrow into sand ranged from 15cm/s (amplitude period: 4s) to 20cm/s (8-12s) for the clams with shell length of 4-10mm, and from 20cm/s (4s) to 25cm/s (8-12s) for the clams with shell length of 16-42mm.
