Map of the Banzu tidal area. The licensed areas are spatially divided into three areas: culture area, where clams are restocked with transplanted seed clams; leisure harvested area, which are open seasonally to non-professional fisherman that pay a harvest charge; fishery area (the rest of the area), for harvest of wild clams. Spatial density of the clams was monitored in 51 sites (filled circle) in the culture area in 1988–2014. Numerals on the chart indicate water depth (m) during the mean low water level of the spring tide.