Upon construction of Grand Coulee Dam in the late 1930’s, salmon were extirpated from almost half of the available habitat in the Columbia River basin. Now, the Upper Columbia United Tribes (UCUT) are leading an effort to reintroduce anadromous salmon back into those historic habitats. The program is considered the largest salmon reintroduction effort in the world, and is in coordination with federal, state, and local governments, along with other tribes in the US and in Canada. Multiple studies are underway to determine productivity, survival, and behavior of Chinook and Sockeye salmon in the blocked area. These studies are intended to inform fish passage at five hydroelectric projects in the US, and to monitor habitat use by anadromous salmon.