There is a growing demand to consider a riverbed as a factor to evaluate fish habitat in river management.This requirement arose because various sediments augmentation expecting riverbed restoration has beenplanned in gravel-bed rivers, especially in the downstream reaches of dams. In this study, sand cover rate(SCR) was defined as an indicator of the riverbed and for the focal point of ayu (Plecoglossus altivelis) inspatial distribution. The results indicated that ayu preferred SCR of 0.15-0.50, especially 0.20-0.25. Twotypes of the composite suitability index (CSI) model and generalized linear model (GLM) were developedconsidering the hydraulic quantities with SCR and without SCR, respectively. The models with SCR werefound to improve calculation sensitivity, and SCR is the most influencing factor in the GLM to explain the ayu presence probability |