LARGE-SCALE HABITAT POTENTIAL EVALUATION FOR AN ENDANGERED SUBSPECIES OF JAPANESE SWEETFISH

Abstract

In the planning of a conservation program, it is important to evaluate the habitat potential at not only a local scale but also a large scale. Our target species, Ryukyu-Ayu, inhabits only Amami-Oshima Is., and it has a distinct regional population that inhabits Okinawa Is., which is located south of Amami-Oshima Is. To evaluate the habitat potential, a model for explaining the record of inhabitation was constructed using generalized liner model (GLM).

Three variables were adopted in this model: watershed area, altitude-compensated air temperature, and inner bay area. The calculation result obtained using the model showed that the index of habitat potential where the target species inhabits Amami-Oshima Is. is ~90%, and that for Okinawa Is. is at most ~60%. The result of the sensitivity analysis for offset the temperature showed that the index for Okinawa Is. can change more sharply than that for Amami-Oshima Is. The amount of offset when the indexes reach 90% can be considered suitable; this corresponds to the rise in seawater temperature.