A Trap for Handling Adult Anadromous Salmonids at Lower Granite Dam on the Snake River, Washington

During the winter of 1995 and spring of 1996, the trapping facility in the fish ladder at Lower Granite Dam on the Snake River was modified to create a system that permits processing large numbers of adult fish while minimizing stress caused by handling. This was accomplished primarily by incorporating a gravity-flow dewatering system into the trap. Adults passing up the fish ladder can be sampled randomly or with the use of diversion systems that sample for coded wire or passive integrated transponder tags. About 13% of the 1,060,059 adult Pacific salmon Oncorhynchus spp. and steelhead O. mykiss that passed through the facility from 1996 through 2001 were diverted for various research collections and observations.