The Snake River smolt trap is a dipper trap that is 90-feet long. Dipper traps are ideal when there is less river flow to guide the fishes into the trap. This is the situation at the head of the Lower Granite Dam Reservoir during the beginning of the spring trapping season.
How are fish dipped out of the water? As fish are migrating downstream, they enter the trap at the upstream side and are guided towards the dipper by wooden weir panels called louvers. Then, they are captured by a rotating dipper that sends them into a water-filled pipe that shuttles them to a livewell. The fishes are automatically scanned for PIT tags as they travel through the pipe, 24 hours per day and 7 days per week, to determine their travel time.
Fish are netted, sampled, some are PIT-tagged, and all are returned to the river to continue their downstream migration to the Pacific Ocean.
This trap operates from early March until late May each year. It has been at its current location below the Interstate ("Blue") Bridge near Lewiston, Idaho since 1984. It was located downstream, at the Red Wolf Bridge, in 1983.
Idaho Department of Fish and Game and the Fish Passage Center cooperatively operate this fish trap as a key component of the Smolt Monitoring Program and the Comparative Survival Study. More information about these important wild salmon and steelhead trout projects is available at https://www.fpc.org/fpc_homepage.php
For more information on Idaho's wild salmon and steelhead click here.