It has been 20 years since the environmental and fisheries problems in the Ariake Sea were reported. However, several
problems including the decrease of bivalve catch（pen shell, ark shell and manila clam）, decrease of macro benthos, and the
occurrence of hypoxia and red tide are ongoing. The fundamental measures required to restore the marine environment are still
unknown. In this article, we overview the environmental and fisheries problems in the Ariake Sea and review the studies about
the long-term changes in tide and tidal current, hypoxia, red tide, and fish catch, and discuss future restoration measures.