Steelhead trout and salmon are anadromous fish, meaning they are born in freshwater, migrate to the ocean, and return to freshwater as adults to spawn. The streams of Napa, Sonoma, and Mendocino Counties historically supported large numbers of steelhead trout, Chinook salmon, and coho salmon. Although their populations have declined sharply in the past several decades, landowners, public agencies, and other organizations are now collaborating to protect and improve their habitat by removing passage barriers, reducing water pollution, and revegetating riparian corridors.