Abstract
This study pays attention to Deiratonotus japonicus in the Kita River, Kyushu.Field surveys and laboratory experiments were carried out to grasp the factors from whichthe number of individuals changes, changes of the total number of the indeviduals and theconditions on habitation. Conclusions in this study are as follows:(1) D. japonicus mainlydistributes in the range from 4.8km to 6.4km from the river mouth;(2) The number change ofindividuals was characterized;(3) If D. japonicus can hide inside riverbed materials, it canbear the flow passing over the riverbed materials; and (4) D. japonicus eggs were hatchedand its early zoeal stage was shown.
