ヤマトシジミの生息域として見た菊池川河口域の環境変遷と修復の可能性評価;ヤマトシジミの生息域として見た菊池川河口域の環境変遷と修復の可能性評価;Estimation of the Succession and Possibility of Restoration in Riverine Estuary of the Kikuchi River from the View of the Habitat of Corbicura Japonica