Monday, September 13, 2010
Hall B (Convention Center)
Endangered bull trout Salvelinus confluentus in the Pend Oreille basin of Idaho and Washington, U.S.A. historically exhibited a diversity of life history migrations; however, hydroelectric dams have since blocked major river migration routes, which threaten diversity. To understand and potentially mitigate these impacts, two ongoing studies at Albeni Falls Dam (AFD) on the Pend Oreille River have focused on: 1) verifying the origins of bull trout entrained by AFD and 2) quantifying the movements of entrained fish to investigate passage options. Five bull trout entrained by AFD have been implanted with radio tags and released upstream of AFD to verify their spawning tributary and 12 tagged bull trout have been released downstream of AFD to determine dam-approach movement behaviors. All upstream-released fish were genetically determined to be from upstream tributaries; two bull trout have been detected entering these tributaries. Bull trout released downstream of AFD exhibited active searching behavior and explored all sections of the dam. Study results confirm that bull trout entrained by AFD are from upstream tributaries, verifying the need to restore passage, and that bull trout encountering the downstream-side of AFD actively seek passage, indicating that fish would likely find a passage structure if it were available.