Our target species, Ryukyu-Ayu (Plecoglossus altivelis ryukyuensis) are thought that they are facing on distinct because of high water temperature in estuary of their habitat on their juvenile stage. It is necessary for conservation to evaluate how that condition effect on Ryukyu-Ayu. The aim of this study is to investigate an impact on their habitat suitability caused by development in estuary. To evaluate this we tried to apply the result of survival experiment on Ryukyu-Ayu larva to actual sites. This means we built statistical model to estimate 24 hours survival rate (ESR) from the experiment results and calculate ESR using field observation data of water temperature and salinity. The results show The ESR in habitat of artificial estuary is less than 40% even though more than 80% in all observation point in natural estuary and that carry out 1 deg water temperature falling can provide about 20% ESR rising.
