AN IMPROVEMENT OF MIGRATION RATE WITH EVASION COLOR OF PLECOGLOSSUS ALTIVELIS ALTIVELIS IN POOL-AND-WEIR FISHWAY

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. On the other hand, it is pointed out that the fish behavior is affected by the wall color. Unfortunately, the effect of wall color in the fishway on the fish behavior has not been investigated. It has been found that ayu (Plecoglossus Altivelis Altivelis) evade red (5R4/14). In this study, the position where painted red were changed into pool side-wall and bed. It was found that the migration rate increases by painting downstream and left bank sidewall. It’s because ayu evaded painted sidewall and center of fish’s school is located nearby upstream notch.