Benefits of Prescribed Flows for Salmon Smolt Survival Enhancement Vary Longitudinally in a Highly Managed River System

Courter, Ian I.; Garrison, Thomas M.; Kock, Tobias J.; Perry, Russell W.; Child, David B.; Hubble, Joel

doi:10.1002/rra.3066

Cited by 9 publications

(13 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Moreover, we observed that higher flow at the reach scale had a more positive effect on survival in dry years with low flow than it did in wet years with high flow. Although the interaction between annual flow and intra‐annual reach flow occurs with one high‐flow year observed in 2017 (Figure 5), similar observations have been made in previous work on late‐fall‐run Chinook Salmon (Courter et al 2016; Perry et al 2018; Henderson et al 2019). Anomalous wet years like 2017 are important to consider because California remains in a state of extended drought, and obtaining data for years like this is likely to be difficult given their importance for fish survival.…”

Section: Discussionsupporting

confidence: 87%

“…Interannual reach flow was calculated by standardizing flow to each reach’s mean flow:

z_{inter, d, y, k} = \frac{Q_{d, y, k} - {normalμ}_{k}}{σ_{k}},

whereas intra‐annual flow was calculated by standardizing daily flow within each reach and year:

z_{intra, d, y, k} = \frac{Q_{d, y, k} - {normalμ}_{y, k}}{σ_{y, k}},

where

z_{inter, d, y, k}

and

z_{intra, d, y, k}

are the inter‐ and intra‐annual reach flows on day d in year y and reach k ;

Q_{d, y, k}

is discharge;

μ_{k}

and

μ_{y, k}

are the means of

Q_{d, y, k}

for each reach and each reach and year, respectively; and

σ_{k}

and

σ_{y, k}

are the SDs of

Q_{d, y, k}

for each reach and each reach and year. Including intra‐annual reach flow allowed us to examine whether large freshet events within a reach would increase survival relative to the mean flow for that year (Cavallo et al 2013; Courter et al 2016). We included intra‐annual reach flow in models with mean annual flow at Bend Bridge because scaling intra‐annual flow by both year and reach removes the effect of annual differences in intra‐annual reach flow, thus eliminating correlation between these variables.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Factors Affecting Spatiotemporal Variation in Survival of Endangered Winter‐Run Chinook Salmon Out‐migrating from the Sacramento River

Hassrick

Ammann

Perry

et al. 2022

N American J Fish Manag

View full text Add to dashboard Cite

Among four extant and declining runs of Chinook Salmon Oncorhynchus tshawytscha in California's Central Valley, none has declined as precipitously as the Sacramento River winter run. Migratory winter-run Chinook Salmon employ a life history strategy to reside and feed in stopover habitats on their way from freshwaters to the ocean. Migratory winter run, on their way from freshwaters to the ocean, employ a life history strategy to reside and feed in stopover habitats that have been affected by anthropogenic disturbance. Using acoustic telemetry, we examined conditions that influenced reach-specific movement and survival of out-migrating juveniles during a prolonged, multi-year drought from 2013 to 2016, followed by one of the wettest years on record (2017). We modeled how time-varying individual riverine covariates and reach-specific habitat features influenced smolt survival. Model selection favored a model with mean annual flow, intra-annual deviations from the mean flow at the reach scale, reach-specific channel characteristics, and travel time. Mean annual flow had the strongest positive effect on survival. A negative interaction between mean annual flow and intra-annual reach flow indicated that within-year deviations at the reach scale from annual mean flow had larger effects on survival in low-flow years. These factors resulted in higher survival during years with pulse flows or high flows. Changes in movement behavior in response to small-scale changes in velocity were negatively associated with survival. Covariates of revetment and wooded bank habitat were positively associated with survival, but the effect of these fixed habitat features changed depending on whether they were situated in the upper or lower part of the river. Fish exhibited density-dependent stopover behavior, with slowed downstream migration in the upper river in the wet years and extending to the lower river in the most critically dry year. This paper contributes two key findings for natural resource managers interested in flow management and targeted habitat

show abstract

Section: Discussionsupporting

confidence: 87%

“…Interannual reach flow was calculated by standardizing flow to each reach’s mean flow:

z_{inter, d, y, k} = \frac{Q_{d, y, k} - {normalμ}_{k}}{σ_{k}},

whereas intra‐annual flow was calculated by standardizing daily flow within each reach and year:

z_{intra, d, y, k} = \frac{Q_{d, y, k} - {normalμ}_{y, k}}{σ_{y, k}},

where

z_{inter, d, y, k}

and

z_{intra, d, y, k}

are the inter‐ and intra‐annual reach flows on day d in year y and reach k ;

Q_{d, y, k}

is discharge;

μ_{k}

and

μ_{y, k}

are the means of

Q_{d, y, k}

for each reach and each reach and year, respectively; and

σ_{k}

and

σ_{y, k}

are the SDs of

Q_{d, y, k}

Section: Methodsmentioning

confidence: 99%

Factors Affecting Spatiotemporal Variation in Survival of Endangered Winter‐Run Chinook Salmon Out‐migrating from the Sacramento River

Hassrick

Ammann

Perry

et al. 2022

N American J Fish Manag

View full text Add to dashboard Cite

show abstract

“…It is likely that such pulse flows will engendered larger cohort‐wide survival gains than predicted here: Flow pulses are known to promote juvenile Chinook salmon to initiate their downstream migration (Sykes et al 2009), allowing a larger portion of the population to take advantage of the associated improvements in survival. Courter et al (2016) used managed flow releases in the Yakima River, Washington, to show the positive impact of increased flow on Chinook salmon smolt survival, which was then used to implement a minimum flow target. Experimental pulse flows may also help decouple the mechanisms driving increased survival, because increased flows through reservoir releases may not affect temperature and turbidity the same as storm‐related flow increases.…”

Section: Discussionmentioning

confidence: 99%

Nonlinear survival of imperiled fish informs managed flows in a highly modified river

et al. 2021

View full text Add to dashboard Cite

Water is a fundamental resource in freshwater ecosystems, and streamflow plays a pivotal role in driving riverine ecology and biodiversity. Ecologically functional flows, managed hydrographs that are meant to reproduce the primary components of the natural hydrograph, are touted as a potential way forward to restore ecological functions of highly modified rivers, while also balancing human water needs. A major challenge in implementing functional flows will be establishing the shape of the managed hydrograph so as to optimize improvements to the ecosystem given the limited resources. Identifying the shape of the flow-biology relationship is thus critical for determining the environmental consequences of flow regulation. In California's Central Valley, studies have found that increased streamflow can improve survival of imperiled juvenile salmon populations during their oceanward migration. These studies have not explored the potential nonlinearities between flow and survival, giving resource managers the difficult task of designing flows intended to help salmon without clear guidance on flow targets. We used an information theoretic approach to analyze migration survival data from 2436 acoustic-tagged juvenile Chinook salmon from studies spanning differing water years (2013)(2014)(2015)(2016)(2017)(2018)(2019) to extract actionable information on the flow-survival relationship. This relationship was best described by a step function, with three flow thresholds that we defined as minimum (4259 cfs), historic mean (10,712 cfs), and high (22,872 cfs). Survival varied by flow threshold: 3.0% below minimum, 18.9% between minimum and historic mean, 50.8% between historic mean and high, and 35.3% above high. We used these thresholds to design alternative hydrographs over the same years that included an important component of functional flows: spring pulse flows. We compared predicted cohort migration survival between actual and alternative hydrographs. Managed hydrographs with pulse flows that targeted high survival thresholds were predicted to increase annual cohort migration survival by 55-132% without any additions to the water budget and by 79-330% with a modest addition to the water budget. These quantitative estimates of the biological consequences of different flow thresholds provide resource managers with critical information for designing functional flow regimes that benefit salmon in California's highly constrained water management arena.

show abstract

“…In this paper, we more closely examine the underlying components of a flow–survival relationship that was quantified by Courter et al (in press; see also Courter et al ). This study found that survival of juvenile Chinook salmon ( Oncorhynchus tshawytscha ) was positively related to river discharge in the ‘Roza Reach’ of the Yakima River, Washington, USA, an 18‐km section of river downstream of a dam that diverts up to 80% of the river's flow.…”

Section: Introductionmentioning

confidence: 99%

Dam Operations Affect Route-specific Passage and Survival of Juvenile Chinook Salmon at a Main-stem Diversion dam

et al. 2016

Self Cite

View full text Add to dashboard Cite

Diversion dams can negatively affect emigrating juvenile salmon populations because fish must pass through the impounded river created by the dam, negotiate a passage route at the dam and then emigrate through a riverine reach that has been affected by reduced river discharge. To quantify the effects of a main-stem diversion dam on juvenile Chinook salmon in the Yakima River, Washington, USA, we used radio telemetry to understand how dam operations and river discharge in the 18-km reach downstream of the dam affected route-specific passage and survival. We found evidence of direct mortality associated with dam passage and indirect mortality associated with migration through the reach below the dam. Survival of fish passing over a surface spill gate (the west gate) was positively related to river discharge, and survival was similar for fish released below the dam, suggesting that passage via this route caused little additional mortality. However, survival of fish that passed under a sub-surface spill gate (the east gate) was considerably lower than survival of fish released downstream of the dam, with the difference in survival decreasing as river discharge increased. The probability of fish passing the dam via three available routes was strongly influenced by dam operations, with passage through the juvenile fish bypass and the east gate increasing with discharge through those routes. By simulating daily passage and route-specific survival, we show that variation in total survival is driven by river discharge and moderated by the proportion of fish passing through low-survival or high-survival passage routes.

show abstract

Benefits of Prescribed Flows for Salmon Smolt Survival Enhancement Vary Longitudinally in a Highly Managed River System

Cited by 9 publications

References 28 publications

Factors Affecting Spatiotemporal Variation in Survival of Endangered Winter‐Run Chinook Salmon Out‐migrating from the Sacramento River

Factors Affecting Spatiotemporal Variation in Survival of Endangered Winter‐Run Chinook Salmon Out‐migrating from the Sacramento River

Nonlinear survival of imperiled fish informs managed flows in a highly modified river

Dam Operations Affect Route-specific Passage and Survival of Juvenile Chinook Salmon at a Main-stem Diversion dam

Contact Info

Product

Resources

About