Regarding the larvae of clam Ruditapes Philippinarum (asari clam) in Tokyo Bay, the advection, dispersion and mutual supply of asari clam was simulated by using a numerical model. With the supply status of asari clam as an index, the influence between the habitats of asari clam could be clarified quantitatively. From these results, several habitats of asari clam could be confirmed as places of stable asari clam reproduction. We also propose sea areas as possible habitats for asari clam in Tokyo Bay. These results could propose important indexes for conserving and establishing the habitats of asari clam and for planning and constructing shallow waters and tidal flats.
In recent years, such environments constituting the foundation of coastal ecosystems as tidal flats, underwater seaweed beds and coral reefs are in a critical situation due to a drastic decrease of asari clam and other bivalve resources and serious deterioration and loss including rocky shore denunciation and coral bleaching. Regarding Tokyo Bay, almost all coasts in the bay were tidal flats at the beginning of the 20th century. However, 90% or more of the tidal flats have been lost to date by reclamation. The great loss of tidal flats seems to have directly led to the reduction of the habitats of organisms living on tidal flats. While causing the variety of species to diminish, this loss may have also greatly reduced the amount of organisms, the production output, and also the purification function. The asari clam, which represents bivalves on tidal flats, is a shellfish indispensable for dishes in Japan and is also confirmed to play an important role in the purification function of tidal flats. In their initial stage, the larvae of asari clam float in the sea for a period of time and have almost no swimming power.