Title

Reconnecting the lower Clark Fork River/ Lake Pend Oreille system: Adult bull trout response to transport above Cabinet Gorge Dam

Abstract

Electrofishing and a fish ladder/trap were used to capture 129 individual adult bull trout Salvelinus confluentus in the Clark Fork River downstream of Cabinet Gorge Dam, Idaho, from 2001 through 2004. A portion of these fish were presumed to have migrated downstream as juveniles from Montana tributaries through or over the dam and reared in Lake Pend Orielle, Idaho (16 kilometers downstream of Cabinet Gorge Dam). Captured adult bull trout were surgically implanted with radio transmitters and were transported upstream by fish tank truck to Cabinet Gorge Reservoir, Montana. Of the 129 individual bull trout successfully released in Montana, 78 were detected in tributaries to Cabinet Gorge Reservoir during the 2001 through 2004 spawning seasons (i.e. September and October). A total of the 26 bull trout transported from Idaho were recaptured in spawning tributaries, transported downstream, and released in the Clark Fork River, Idaho. Another 43 bull trout were documented to have volitionally passed downstream through turbines or over Cabinet Gorge Dam, a minimum of 42 of those likely survived turbine passage. Genetic assignments to tributaries of origin were accomplished for most fish captured over the 4 year study period. Of the 112 viable genetic samples collected below Cabinet Gorge Dam, 90% were assigned to upstream tributaries. Radio receivers at Noxon Rapids Dam (31 kilometers upstream from Cabinet Gorge Dam) detected 40 of the 129 bull trout in the dam tailrace area, 70% of these fish originated upstream of Noxon Rapids Dam, the second dam on the Clark Fork River.

Start Date

1-4-2005 1:00 PM

End Date

1-4-2005 3:00 PM

Document Type

Poster

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Apr 1st, 1:00 PM Apr 1st, 3:00 PM

Reconnecting the lower Clark Fork River/ Lake Pend Oreille system: Adult bull trout response to transport above Cabinet Gorge Dam

Electrofishing and a fish ladder/trap were used to capture 129 individual adult bull trout Salvelinus confluentus in the Clark Fork River downstream of Cabinet Gorge Dam, Idaho, from 2001 through 2004. A portion of these fish were presumed to have migrated downstream as juveniles from Montana tributaries through or over the dam and reared in Lake Pend Orielle, Idaho (16 kilometers downstream of Cabinet Gorge Dam). Captured adult bull trout were surgically implanted with radio transmitters and were transported upstream by fish tank truck to Cabinet Gorge Reservoir, Montana. Of the 129 individual bull trout successfully released in Montana, 78 were detected in tributaries to Cabinet Gorge Reservoir during the 2001 through 2004 spawning seasons (i.e. September and October). A total of the 26 bull trout transported from Idaho were recaptured in spawning tributaries, transported downstream, and released in the Clark Fork River, Idaho. Another 43 bull trout were documented to have volitionally passed downstream through turbines or over Cabinet Gorge Dam, a minimum of 42 of those likely survived turbine passage. Genetic assignments to tributaries of origin were accomplished for most fish captured over the 4 year study period. Of the 112 viable genetic samples collected below Cabinet Gorge Dam, 90% were assigned to upstream tributaries. Radio receivers at Noxon Rapids Dam (31 kilometers upstream from Cabinet Gorge Dam) detected 40 of the 129 bull trout in the dam tailrace area, 70% of these fish originated upstream of Noxon Rapids Dam, the second dam on the Clark Fork River.