The objectives of this project are to design, prototype, and perform laboratory and field tests of an injectable, acoustic micro-transmitter that can be used to study the behavior and survival of sensitive fish species (specifically juvenile eel and lamprey initially). Additionally, the project will provide information to develop mitigation measures for safer passage of eel and lamprey and reduce the environmental impacts hydropower production has on these species. Future research could build on this project, expanding the use of the tiny tags to many other species, such as American shad, delta smelt, and river herring. This project is a partnered research effort with the U.S. Army Corps of Engineers under the Memorandum of Understanding for Hydropower.