Abstract
Many surveys regarding the ascending juvenile ayu Plecoglossus altivelis and the descending larval ayu have been conducted, in the wake of the construction of the Nagaragawa Estuary Barrage. By statistically analyzing the relationship between those survey results and the ecological characteristics of ayu and physical environment factors, we found that the river discharge from the spawning season to the descending season of ayu and the water temperature in the sea-dwelling season of juvenile ayu affect the variation of ascending juvenile ayu in the Nagara River. Thus our regression model would be able to forecast the ascending ayu population in terms of merely environmental factors.
