Snake River Stream-Type Chinook Survival Rates and Impacts of Hydropower System on Early Ocean Mortality

The relationship of Snake River stream-type Chinook survival rates to in-river, ocean and climate conditions Howard Schaller, USFWS * Charlie Petrosky, IDFG NPCC Science/Policy Workshop - September 12, 2007

Snake River Salmon and steelhead declined since completion of hydrosystem Survival declines for stream-type Chinook were in the Smolt-to-adult life stage

Is there evidence linking estuary and early-ocean mortality to the migration experience through the hydrosystem? THE Critical Uncertainty that differentiated risk levels amongst options in the 2000 Biological Opinion hydro delayed mort bad future climate/ ocean ocean regime delayed mort Stock viability delayed mort median hydro delayed mort ocean regime delayed mort good future climate/ ocean Stock viability delayed mort mean (Peters and Marmorek 2001; Karieva et al. 2000; Wilson 2003)

Different passage routes over, through, or around dams • Transport via barge and truck: • Bypass facility stress • Can not separate species • Disease exposure • Change estuary arrival timing Inriver migrantsalso face challenges from the altered migration route

Hydrosystem effects on Smolt to Adult Survival Rates (SARs) • In-river migrants: • Fish condition • injury, stress, bioenergetics • Delayed migration • bioenergetic costs • physiological state vs. arrival timing • miss optimal environmental conditions • Mostly indirect inferences • Transported • Measurable (relative) • survive ~½ as well as in-river migrants in ocean (D ~ 0.5) Mortality within the hydrosystem (measurable) Mortality in Estuary/Early Ocean life stages Berggren et al. (2006); Budy et al. (2002)

Multiple Analytical Methods for mortality inferences • Compare Spawner-Recruit residuals • upriver vs. downriver populations • Multi-stock S-R models • differential and common mortality estimates between upriver & downriver populations • Compare SARs • PIT tags, upriver vs. downriver populations • Multiple regression • upriver populations only vs. migration & ocean conditions

Spatial/temporal comparisonsSpawner-Recruitmodels using downriver populations Downriver populations Snake River ESU

Downriver populations Spawner-recruit analyses • Snake R. survive ¼ to 1/3 as well as downriver since dams • Common annual mortality patterns between upriver & downriver populations • Common year effects correlate with good and poor ocean conditions Snake River populations Schaller et al. (1999); Deriso et al. (2001);Schaller and Petrosky (2007)

PIT tag SAR comparisons wild Snake and John Day stream-type Chinook, 2000-2004 Downriver populations Snake River ESU Comparative Survival Study: CSS 10-year Report (2007)

PIT tag studies: • Downriver SARs are 3-4X Snake SARs • Snake River SARs generally < 2 to 6% SAR CSS 10-year Report (2007)

Spawner-Recruit analysis vs SAR comparisons: estimated difference in mortality Snake vs. downriver • Snake River survival 1/3 to ¼ survival of John Day populations CSS 10-year Report (2007); Schaller and Petrosky (2007)

Multiple Regression for Snake River alone1st year ocean survival (s3 in Zabel et al. 2006)Environmental variables: migration corridor & oceanModel selection criteria: AIC and BIC

Water Travel Time: Lewiston to Bonneville Dampre-dam ~2 days; current ~ 19 days (10-40 days) 1938 (BON), 1953 (MCN), 1957 (TDD), 1961 (IHR), 1968 (JDA), 1969 (LMN), 1970 (LGS), 1975 (LGR)

Pacific Decadal Oscillation • Interdecadal climate variability in the North Pacific – (Sea Surface Temperature) • Coastal Upwelling Index • based upon Ekman's theory of mass transport due to wind stress - 45oN – (productivity) • “Good Ocean” • Cool phase PDO • April Upwelling • Oct Downwelling Coastal Upwelling Process

Pre-dam. WTT Current WTT Expected change in 1st year ocean survival vs. WTT, Sept. PDO & Apr. UpwellingResponse to WTT - similar to results using upriver/downriver populations Best fit (adj. R2=0.71), simplest model (best BIC)

Survival Patterns for Snake Populations • Multiple Regression Analysis: WTT was a variable that consistently explained patterns in various survival metrics • These measures of survival were best described by WTT during smolt migration and ocean/climatic variables • Stream-type Chinook S3 • Stream-type Chinook SARs • Stream-type Chinook R/S • Steelhead S3 • Steelhead SARs

Summary • Upriver/downriver population performance indicates the hydrosystem is a key factor influencing early ocean mortality • Analyses of only Snake River populations - a significant component of early ocean survival is related to impacts of the dams • Magnitude of hydrosystem related early ocean mortality ~ similar to other methods

Conclusions • Multiple lines of evidence indicate mortality in the early ocean life stage is related to cumulative impacts of the hydropower system • Recovery efforts need to address these cumulative impacts

Snake River Stream-Type Chinook Survival Rates and Impacts of Hydropower System on Early Ocean Mortality