EFFECTS OF BOULDER INTERVAL OVER POOL BED IN POOL-AND-WEIR FISHWAY ON MIGRATION RATE OF OPSARIICHTHYS PLATYPUS

Abstract

 It is important to keep suitable area by boulder in pool-and-weir fishway to make the migration rates of fish high. In this study, migrating behaviors of Oikawa (Opsariichthys platypus) in pool-and-weir fishway were compared with interval of boulders placed on the bottom of pool-and-weir fishway changed. Migration behaviors of Oikawa were obtained with the aid of two sets of digital video cameras. It was found that Oikawa migrates remarkably uses space between boulders with an increase of interval of boulders. It is because the velocity of this space is low as compared with the higher layer. As the result, the migration rate of Oikawa increases with an increase of the boulder interval.