Fragment, travelling and confusion of the recent malacofauna: The Ariake Inland Sea as the representative of a miserable state of the Japanese inner bay malacofauna

The Recent molluscan fauna of the Ariake Inland Sea is well known as comprising of many unique species. Especially it contains the Chinese Continental faunal elements, which are restricted to the innermost parts of a few large bays of Japan. However, most of them have become extinct or endangered in the recent years because of the rapid artificial change of coastal environment including landfilling, reclamations, bank-protection and pollutions and the destructions of habitats. Also, very few faunal surveys were done before the recent major extinction. Therefore the original molluscan fauna of the Ariake Inland Sea still remains obscure (especially in the subtidal zones). On the other hand, several alien species have artificially been introduced from China or Korea with imported edible clams and also widespread to other areas of Japan through the Ariake Inland Sea. Some of these species had been threatened in Japan before the recent intrusion and it is difficult to distinguish the alien populations from the native ones at present because the lacking of enough records of the original fauna. To solve such confusion and to conserve the native fauna, species, and populations, it is pointed out that the most important thing is the detailed faunal survey and databasing based on extant collection of specimens from now on.