Fig 2. Time series of adult steelhead ascending Ice Harbor dam (in natural logarithms). The straight horizontal black lines are the mean values for the periods of 1962-1972 and 1984-1993. The short red vertical lines indicate the dates when four low-head dams (John Day in 68, Lower Monumental in 69, Little Goose in 70 and Lower Granite in 75) were completed and the long red vertical lines the dates the two high-head dams (Hells Canyon 67 and Dwarshak 71) were completed.