INFLUENCE OF WALL COLOR ON MIGRATION CHARACTERISTIC OF PLECOGLOSSUS ALTIVELIS ALTIVELIS

Abstract

 Most of fishways installed in Japanese rivers belong to the pool-and-weir fishway type. This fishway is usually made by concrete, so that the color of the pool side-wall and bed are gray. It has been found that ayu (Plecoglossus Altivelis Altivelis)'s evasion color is red, however, preference color has been unknown. In this study, it have been tried to improve migration rate of ayu with the color of sidewall were changed. It was found that most preference color was yellow for ayu. It was found that the migration rate increases by painting upstream sidewall and right bank sidewall in yellow. It's because ayu prefer painted upstream sidewall and right bank sidewall in yellow, and center of fish's school is located nearby upstream notch.