Abstract
We investigated macrozoobenthos fauna in 26 tidal flats existing in foreshores, lagoons, tidal rivers and small artificial channels along the entire coast of Tokyo Bay to evaluate the distribution and population rarity of the tidal flat species. A total of 98 species were recorded, of which 31 were regarded as rare species that need to be conserved. The rare species were found mainly in artificial channels with a salt marsh. Among these rare species, the mud snails Batillaria multiformis, Cerithidea rhizophorarum, and Cerithideopsilla djadjariensis; the varunid crabs, Chasmagnathus convexus and Helicana japonica; the sesarmid crab Sesarmops intermedium; and the camptandriid crab Deiratonotus cristatus are considered rare not only in Tokyo Bay, but also along the coasts of the Japanese main islands, suggesting these species should be the first focus of conservation. Furthermore, the occurrence of rare species tended to be restricted to the eastern shore of Tokyo Bay, where tidal flats (Obitsu Estuary, Edogawa Drain and Tamagawa River) and artificial channels with a salt marsh are located. From the viewpoint of ecological connectivity between the tidal river and the artificial channels, these findings suggest that restoration of tidal flats with salt marshes along the shoreline of the bay is important to conserve the biodiversity of tidal-flat macrozoobenthos in Tokyo Bay.
