EFFECTS OF SLOPE AND SPACES OF BUNCH OF BRUSHES IN FISH LADDER FOR EELS ON MIGRATION RATE OF Anguilla japonica

Abstract

 It is estimated that the number of eels (Anguilla japonica) is decreased by the worse of river environment, so fish ladder for eels is necessary in the river. Bunch of burshes or grass are put on fish ladder for eels. However, little is known about typical space, diameter of bunch of brushes and migrating characteristics of eels. This study was made to evaluate the migration rate of eels under the condition that slope and space of bunch of brushes in fish ladder are changed. As a result, it was found that migration rate decreases with an increase of slope and space of bunch of brushes. On the other hand, it was proven that sinuosity of eels and averaged migrating speed tend to increase. Besides, it was confirmed that eels migrated with getting caught by brushes and on the brushes to the upside.