Before irrigation development, the San Joaquin River and its tributaries once supported the third largest run of Pacific salmon in California including prodigious spring, summer, fall, and late-fall runs of chinook salmon. The California Department of Fish and Game estimated in the 1930s that the historic salmon run was likely in the vicinity of 200,000 to 500,000 of spawners annually, but by the mid-20th century, reduction in river flows led to the run dropping to about 3,000-7,000. Some sources put the historic populations as high as three hundred thousand, but this is highly unlikely because of the limited habitat available in the watershed.