The Stanislaus River provides habitat for native anadromous fish, particularly Chinook (king) salmon, and steelhead, which spend their adult lives in the ocean but must return to fresh water to spawn. In its natural state the Stanislaus had a major spawning run in the late spring (April–June) and smaller runs in the fall and winter. The construction of Goodwin Dam in 1913 blocked migration to about half of the available spawning habitat in the Stanislaus River basin, and populations have declined thereafter, especially since the construction of the Melones and Tri-Dam projects which changed the flow pattern in the Stanislaus River. Between 1952 and 2015, the fall chinook population has ranged from a high of 35,000 in 1953 to zero in 1977. The average fall chinook number in the 21st century has been 3,558 fish.