Post-Release Attributes and Survival of Hatchery and Natural Fall Chinook Salmon in the Snake River; 2000-2001 Annual Report.

Connor, William P.

doi:10.2172/812365

Cited by 1 publication

(3 citation statements)

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“…Consequently, water temperatures during the egg incubation period (~December-May) may have been relatively warmer in the historic production areas than in the current spawning areas. This difference in temperature regimes may be the reason that fall Chinook salmon from current production areas in the Hells Canyon Reach arrive at the Lower Granite Dam section of the Snake River 1 to 4 weeks later than they did before development of the Hells Canyon Complex and the four lower Snake River projects operated by the U.S. Army Corps of Engineers (NMFS 2000a;Connor et al 2001). …”

Section: Introductionmentioning

confidence: 99%

“…The shift toward later emergence and migration requires smolts to migrate through downstream reservoirs during mid-to late-summer when environmental conditions are unfavorable for survival (Connor et al 2001). The differential survival among cohorts of wild Snake River subyearling juvenile Chinook can be traced back to emergence timing, with earlier emerging fish migrating earlier through Lower Granite Reservoir under conditions of higher flows and cooler water temperatures than later emerging fish (Connor 1999).…”

Section: Introductionmentioning

confidence: 99%

“…The differential survival among cohorts of wild Snake River subyearling juvenile Chinook can be traced back to emergence timing, with earlier emerging fish migrating earlier through Lower Granite Reservoir under conditions of higher flows and cooler water temperatures than later emerging fish (Connor 1999). Later migration puts juvenile migrants in reservoirs during periods when water temperatures approach Chinook salmon's thermal tolerance (NMFS 2000a).…”

Section: Introductionmentioning

confidence: 99%

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Effects of Hyporheic Exchange Flows on Egg Pocket Water Temperature in Snake River Fall Chinook Salmon Spawning Areas, 2002-2003 Final Report.

Hanrahan¹,

Geist²,

Arntzen

2004

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SummaryThe development of the Snake River hydroelectric system has affected fall Chinook salmon smolts by shifting their migration timing to a period (mid-to late-summer) when downstream reservoir conditions are unfavorable for survival. Subsequent to the Snake River Chinook salmon fall-run Evolutionary Significant Unit being listed as Threatened under the Endangered Species Act, recovery planning has included changes in hydrosystem operations (e.g., summer flow augmentation) to improve water temperature and flow conditions during the juvenile Chinook salmon summer migration period. In light of the limited water supplies from the Dworshak reservoir for summer flow augmentation, and the associated uncertainties regarding benefits to migrating fall Chinook salmon smolts, additional approaches for improved smolt survival need to be evaluated.This report describes research conducted by the Pacific Northwest National Laboratory (PNNL) that evaluated relationships among river discharge, hyporheic zone characteristics, and egg pocket water temperature in Snake River fall Chinook salmon spawning areas. This was a pilot-scale study to evaluate these relationships under existing operations of Hells Canyon Dam (i.e., without any prescribed manipulations of river discharge) during the 2002-2003 water year. The project was initiated in the context of examining the potential for improving juvenile Snake River fall Chinook salmon survival by modifying the discharge operations of Hells Canyon Dam. The potential for improved survival would be gained by increasing the rate at which early life history events proceed (i.e., incubation and emergence), thereby allowing smolts to migrate through downstream reservoirs during early-to mid-summer when river conditions are more favorable for survival.PNNL implemented this research project at index sites throughout 160 km of the Hells Canyon Reach (HCR) of the Snake River. The HCR extends from Hells Canyon Dam (river kilometer [rkm] 399) downstream to the upper end of Lower Granite Reservoir near rkm 240. We randomly selected 14 fall Chinook salmon spawning locations as study sites, which represents 25% of the most used spawning areas throughout the HCR. Interactions between river water and pore water within the riverbed (i.e., hyporheic zone) at each site were quantified through the use of self-contained temperature and water level data loggers suspended inside of piezometers. Surrounding the piezometer cluster at each site were 3 artificial egg pockets. In mid-November 2002, early-eyed stage fall Chinook salmon eggs were placed inside of perforated polyvinyl chloride (PVC) tubes, along with a temperature data logger, and buried within the egg pockets. Fall Chinook salmon eggs were also incubated in the laboratory for the purpose of developing growth curves that could be used as indicators of emergence timing. The effects of discharge on vertical hydrologic exchange between the river and riverbed were inferred from measured temperature gradients between the river and riverbed, and the app...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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