Reed field, tidal flat and seagrass beds are essential components of coastal ecosystem. Field observations were conducted in Ena Bay and Kanazawa-hakkei Estuary which include the three components. Habitat suitability index models for reed and fiddler crab were developed, which were selected as the representative organisms of reed field and tidal flat respectively. Observed data on seagrass beds indicated the environmental requirements of eelgrass. Some organisms use the different fields according to each stage of their life cycle and to each living activity such as feeding, spawning, etc. These habitat requirements tell that it must be necessary not only to understand ecology in each field but also to establish their ecological relations of components to restore the coastal nature.
