Abstract
AMPARU is a large tidal lagoon located on the west coast of Ishigaki Island, where a variety of small crabs range over. In these thirty years, however, accumulation of red clay from the watershed has been changing the topography and the hydraulic characteristics of the lagoon, and then changing the environments for the crabs to habitat there. This paper presents a result of a field survey to understand the spatial distribution of crabs in relation with the conditions of bed materials and hydraulic characteristics in the lagoon. First, spatial distribution of four kinds crabs are clarified through quadrat survey and burrow survey. Then, Habitat evaluation model of two predominant crabs are constructed based on statistical method. Their habitat decision is basically highly related to feeding activity. However, Ghost crab which is predominant throw a year is affected by distribution of fiddler crabs.
