Abstract
Relationships between the sediment hardness and the upper distribution limit of the burrowing amphipod Haustorioides japonicus were examined on 18 sandy shores in Niigata and Toyama prefectures, on the Japan Sea coast. Sediment hardness was measured by three methods (using a vane tester, a digital force gauge, or a cone penetrometer) and compared with the estimates from a previous laboratory experiment. Results showed that the vane tester measurements of the hardness of the sandy sediment corresponding to the upper distribution limit on the shores represented a similar value to the measurement obtained in the laboratory. Some similarities between the measurement mechanisms of the vane tester and the burrowing behavior of the amphipods may explain the results. Consideration of the mechanism of hardness measurement will improve understanding of the relationships between sediment hardness and the distribution of burrowing animals on sandy shores.
