This project will be conducted by the US Geological Survey (USGS), US Fish and Wildlife Service (USFWS), Pacific Northwest National Laboratory (PNNL), and the University of Washington (UW). The goal of this project is to provide empirical data and analyses on the dam passage timing, travel rate, survival, and life history variation of fall Chinook salmon juveniles passing downstream in the four lower Snake River reservoirs from spring to winter.  The lack of this information has made it difficult to plan and evaluate aspects of hydrosystem operation including transportation and the timing and location of summer spill.  We propose to use radio telemetry, acoustic telemetry, and PIT tags to study migratory behavior, survival, and life history.  Subyearling fall Chinook salmon will be collected and tagged monthly from May through November in the Snake and Clearwater rivers.  We will use radio telemetry to collect migration behavior and passage timing information.  We will use acoustic telemetry to measure survival and determine where and when fall Chinook salmon juveniles stop migrating and begin to exhibit the reservoir-type life history.  We will collect water velocity and temperature information throughout the reservoirs and use hydrodynamic modeling to characterize the environmental conditions where fish are located.  This will be done by linking observed patterns in juvenile fall Chinook salmon behavior with hydraulic data.  We will use a statistical approach to estimate survival of subyearling fall Chinook salmon that exhibit a reservoir life history.  Previously this has not been possible.  The results from this study will assist fish managers in making informed decisions about operating the hydrosystem, including issues associated with juvenile transportation and summer spill.