Relative Survival of Juvenile Salmon Passing through the Spillway of the Dalles Dam, 1999

摘要

High rates of spill are presumed to increase passage survival for juvenile salmonid migrants because passage survival through spillways at Columbia and Snake River dams is generally higher than through turbines. However, two conditions at the Dalles Dam may decrease spill passage survival under high spill conditions: (1) a short stilling basin and shallow tailrace result in severe turbulence and lateral currents that may cause physical injury to migrant salmon; and (2) a large proportion of spillway-passed water moves through shallows and islands downstream, where predation on salmonids by gulls (Larus spp.) and northern pikeminnow (Ptychocheilus oregonensis) may be substantially higher.