Abstract
This study aims to find ways for flushing with a little impact on fishery environment, by field observations and experiments, as the sediment flushing from Dashidaira dam at Kurobe River in December, 1993 caused serious problems for the local fishery.
The impact caused by muddy water density depends on species. No dead case was found for Salvelinus leucomaenis, Oncorhynchus masou, Oncorhynchus keta, Nordotis discus hannai. A Rise in hemoglobin levels was observed for Salvelinus leucomaenis, Oncorhynchus masou, Oncorhynchus keta as muddy water density (SS concentration 8,000 mg/L) increases, while it recovered to normal levels on a day when the SS density decreases. On the other hand, evasive action was observed for Pagrus major, Seriola quinqueradiata, but it went back after the SS density decreased. Sillago japonica, Sebastes schlegeli didn't take any action.
Based on these observations, we concluded that sediment flushing in a dam might be allowed under certain conditions.
