A PROPOSAL OF FISH LADDER WITH TRIANGULAR STRIP ROUGHNESS SUITABLE FOR ANGUILLA JAPONICA MIGRATION

Abstract

 When eels migrate upstream from the ocean to rivers, dams and weirs act as barriers to their migration, and this has a negative impact on the survival of the species. When eels migrate upstream, no significant frictional force is expected to be generated between the eel, which is covered by a mucous membrane, and the bottom surface. Therefore, Onitsuka et al. devised the installation of rectangular strip roughness with no gaps in the transverse direction. However, the upstream corner of the rectangular strip roughness has a gap between the belly of Anguilla japonica and the bottom surface, resulting in a decrease in frictional force. One way to avoid this problem is to use triangular strip roughness. In this study, the spacing of the triangular strip roughness was set to 0.5 times the total length of Anguilla japonica, and the geometrical conditions suitable for the run were sought by varying triangular strip roughness and the slope of the fish ladder. The results showed that under the conditions of this experiment, a triangular strip roughness gradient of 16.7° and a fish ladder gradient of 10° were the most suitable for the 200mm long Anguilla japonica to migrate upstream.