2002 年 66 巻 2 号 p. 88-101
Artificial creation of shallows, including tidal flats and the establishment of sanctuary, is necessary to restore decreasing resources of the bivalves and their related water purification function. Therefore, it is important to choose areas that will be the most effective for the recruitment and/or supply of pelagic larvae. We selected the short-necked clam (Ruditapes philippinarum) as a target species, and observed vertical distribution of the larvae. Using a receptor mode model, we tried to predict trajectories of the pelagic larvae towards the Isshiki tidal flat areas, where is the biggest fishery ground for short-necked clams in Mikawa Bay. The results showed the following: (1) Pelagic larvae are distributed in the mid layer at a depth of about 3m by some autonomous behavior; (2) Relatively stable amount of biomass in the Isshiki tidal flat areas depends on multiple larval supply sources; (3) Sources of supply vary greatly with temporal wind-induced currents; (4) Main sources of larvae supplied to the Isshiki tidal flat areas exist at the inner part of the bay, so there is a great possibility that the larval supply might have been greatly damaged by extensive coastal reclamation in the past, and by the hypoxic conditions in recent years; and (5) Artificial shallows should be constructed at the inner-part of Mikawa Bay so that the small shallows, still in existence at the inner part of the bay, will become more important. The receptor mode model used in this study has been useful in solving some of the difficult problems faced in restoring bay environment, such as, “where is the best location to site artificial shallows and/or protected areas?”
