| A diversion facility installed at reaches upstream of Pirika Dam to generate downstream flow into the fish passage, and allow the fish to migrate to the sea. However, when the flow rate of the diversion facility exceeds 7.00m3/s, there are concerns that masu salmon smolt have trouble reaching the dam reservoir, because the smolt in the dam reservoir cannot migrate to the sea through the diversion facility. A PIT tag system and radio transmitters for biotelemetry was used to evaluate the diversion facility. It was found that 88.2 % of the smolt were able to enter the diversion facility, and 80.4 % of all smolt were able to access the fish passage. It was also clarified that smolt downstream migration had two peaks per day. During the study period, although the flow rate was in the range between 2.21m3/s and 30.4m3/s, the diversion facility was revealed to have satisfactory functionality for the downstream migration of smolt. |
