Large-scale spatial variability of riverbed temperature gradients in Snake River fall Chinook salmon spawning areas

2007 ◽  
Vol 23 (3) ◽  
pp. 323-341 ◽  
Author(s):  
Timothy P. Hanrahan
Keyword(s):  
Spatial Variability ◽  
Chinook Salmon ◽  
Large Scale ◽  
Temperature Gradients ◽  
Snake River ◽  
Spawning Areas

Experimental measurement of hydrosystem-induced delayed mortality in juvenile Snake River spring Chinook salmon (Oncorhynchus tshawytscha) using a large-scale acoustic array

2009 ◽  
Vol 66 (7) ◽  
pp. 1019-1024 ◽  
Author(s):  
Erin L. Rechisky ◽  
David W. Welch ◽  
Aswea D. Porter ◽  
Melinda C. Jacobs ◽  
Adrian Ladouceur
Keyword(s):  
Pacific Ocean ◽  
Chinook Salmon ◽  
Large Scale ◽  
Oncorhynchus Tshawytscha ◽  
Fork Length ◽  
Snake River ◽  
Return Rates ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Delayed Mortality

Out-migrating Snake River salmon smolts must pass eight major hydro dams before reaching the Pacific Ocean. Direct mortality at the dams is generally low; however, the cumulative stress caused by dam passage is hypothesized to result in delayed mortality, which occurs beyond the impounded section of the river. We tested the delayed mortality hypothesis by comparing in-river and early ocean survival of hatchery-origin spring Chinook salmon ( Oncorhynchus tshawytscha ) from the Snake River to a mid-Columbia River population that passes through only four dams and has higher smolt to adult return rates. Smolts >140 mm fork length were implanted with acoustic transmitters and tracked with the Pacific Ocean Shelf Tracking (POST) array to as far as Alaska. There was no detectable difference in survivorship to the first ocean detection line, 274 km beyond the final dam (SSnake = 29% ± 4%, SYakima = 28% ± 5%), indicating that the survival disparity observed in adult return rates may develop later in the marine life history phase. Our study is the first to estimate survival in the coastal ocean and demonstrates the utility of a large-scale array in testing previously intractable hypotheses.

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