OPTIMUM CHANNEL SLOPE AND FISHLADDER LENGTH FOR ANGUILLA JAPONICA MIGRATION

Abstract

 Most fishladders in Japan are designed for swimming fish and are not effective for benthic one such as eels. In Europe, ramp-type fishladders are sometimes installed for eels, but the optimum geometrical shape has not been clarified. In this study, the channel slope and fishladder length were changed. It was found that the migration and success rate decreased with increasing the fishladder length from 0.4 to 2.0m, and the migration rate was about 0.7 for fisladder length between 0.4 and 0.8m when the channel slope was 30 degree. The migration swimming speed and sinuosity increased with increasing the fishladder length, and the stagnation rate decreased. In the range of the experimental conditions, the optimum fishladder length was in the rage between 0.4 and 0.8m and channel slope is 30 degree for the 200mm total length of Anguilla japonica.