Historically, the American River provided approximately 100 miles of stream in which salmon and steelhead could spawn and rear. When the Folsom-Nimbus project was completed in 1958, most of the spawning and rearing areas for the fish were cut off. Nimbus Hatchery was constructed to replace the salmon and steelhead runs that were blocked by Nimbus dam. The Nimbus Fish Hatchery located at Nimbus Dam raises Chinook salmon and steelhead for release to the American River. About 4 million Chinook salmon and 43,000 steelhead are released each year. Educational activities for children and adults are offered. The U.S. Bureau of Reclamation pays the California Department of Fish and Wildlife to operate the hatchery.