Fish passing through hydroturbines and in spill are subjected to conditions that can injure or kill them. Hydroturbines in the Columbia and Snake river hydropower system, in addition to many else-where, are nearing the end of their operational life expectancy. Before rehabilitating or replacing these turbines, new designs for runners and other portions of the turbine system are being considered. Mean-while, spill has been identified as a preferred dam passage alternative for fish. However, questions remain about the optimum structural configuration and operations for safe passage of fish in spill. A major focus of the new designs for turbines and investigation into spill passage conditions is to provide safer downstream passage for fish. To assist in deriving biological specifications for design of turbine rehabilitation measures, new "fish-friendly" turbines, and spillway designs and operations, Pacific Northwest National Laboratory (PNNL) scientists have developed and tested an autonomous multi-sensor device called a Sensor Fish that can acquire pressure and tri-axial linear acceleration data during passage through severe hydraulic conditions. The purpose of the Sensor Fish is to characterize physical conditions fish experience during passage through hydro turbines, spill stilling basins, high-discharge outfalls, and other dam passage routes. Field tests of the Sensor Fish at Rock Island, McNary, The Dalles, Bonneville, and Wanapum dams on the Columbia River and the Prosser Irrigation District on the Yakima River have shown that the device can withstand the severe environments of turbine, spill, and fish bypass passage and provide useful environmental data that can ultimately aid in the design and operation of new and existing turbines, spill, and dam fish bypass facilities.