In order to clarify the relation between the driftwood and the boring and sessile animals and the route of the driftwood, etc., the authors had made a series of marking experiments, releasing the experimental driftwoods of lauan (Fig. 1) in the area southeast of Formosa and in the eastern waters of Mariana Islands. The experimental driftwoods were recovered about 5% (Table 1, Fig.2). As compared with the natural driftwoods, the driftwoods recovered showed a remarkable difference in the appearance (Fig. 3). The fishermens who recovered the experimental driftwwods reported that those woods were not followed by skipjack and tunas at the time of the recovery on the sea.
On the experimental driftwoods recovered in this experiment, the predominance of Teredora aurita which had developed on the natural driftwoods that were followed by skipjack and tunas could not be found, perhaps because the drifting period of the experimental driftwoods was too short. Further on the experimental driftwoods which had been set on the Izu coast for comparison, Lepas anserifera of big shell, Amphipoda sp., and Balanus tintinnabulum which were seen in plenty on the natural driftwoods could not be founn.
Accordingly further studies on the mechanism alluring skipjack and tunas to a driftwood are necessary. To release the experimental driftwoods in more southern seas than the adjacent waters of Formosa and to research the environment of the places where many driftwoods gather by wind or sea current seem also to be necessary.