Pacific States Marine Fisheries Commission biologist Casey Campos looks for evidence of salmon spawning in the Yuba River below Englebright Dam near Smartsville, Calif., Dec. 12, 2011. Under the direction of the National Marine Fisheries Service, the U.S. Army Corps of Engineers Sacramento District, which owns and manages the dam, has placed more than 5,000 tons of gravel in the river to improve spawning habitat for the threatened Chinook salmon and steelhead trout species. The PSMFC is charged with tracking spawning activity related to the new gravel. (U.S. Army photo by Chris Gray-Garcia/Released)