Abstract
Populations of Anguilla japonica have been decreasing in recent years. The reasons of the population decreasing are overfishing of Anguilla japonica, the deterioration of the river environment and so on. However, in the present circumstances, studies on the ecology of eels and fish ladder for eels mostly haven't advanced. Fish ladders for eels have been designed by considering that not only swimming capacity of eels, but also climbing capacity on a slope. In the present study, an investigation on climbing characteristics of Anguilla japonica was conducted under the condition that grain diameter of boulders in slopes are changed at a constant slope. As a result, it was found that climbing success rate is the maximum at 20mm of major axis. Also, Anguilla japonica climbed while using boulders by serpentine movement, and the averaged climbing speed has been decreasing with the increase of major axis.
