Outmigration survival of a threatened steelhead population through a tidal estuary

Buchanan, Rebecca A.; Buttermore, Elissa N.; Israel, Joshua A.

doi:10.1139/cjfas-2020-0467

“…However, route selection at the TCJ appears to be more important, with especially low survival for Turner Cut fish, demonstrating regional differences in mortality risk within the interior Delta (SST 2017). A similar route effect was observed at Turner Cut for steelhead (Buchanan et al 2021).…”

Section: Namesupporting

confidence: 73%

“…SALMON DYNAMICS IN A DATA-LIMITED ENVIRONMENT to population persistence (Crozier et al 2021). However, studying estuarine life stages and identifying their survival patterns can be challenging (Buchanan et al 2021). Opportunities to reevaluate previous findings with new data are rare in ecology, where data collection is arduous and studies are expensive, but they are vital to scientific learning and effective management.…”

Section: Namementioning

confidence: 99%

“…In addition to assessing and updating the original model, the expanded data set provides an opportunity to investigate hypotheses relating to potential interactions between management actions or migration strategies and environmental conditions. For instance, it has been hypothesized that the benefit of the rock barrier results from increased river flow directed down the main-stem SJR (i.e., prevented from entering OR) when the barrier is installed (Buchanan et al 2021). If so, then the effect of increased Delta inflow on survival should be higher when the barrier is in place.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Understanding Salmon Migration Dynamics in a Data‐Limited Environment

Buchanan

¹

,

Whitlock

²

2022

N American J Fish Manag

Self Cite

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Effective management of natural resources and migratory fish populations depends on understanding the relationship between life cycle parameters, management decisions, and environmental conditions. However, the difficulty of data collection can result in small or nonrepresentative data sets, thus limiting the accuracy and utility of modeling results. This is especially true for studies of migratory species in changing environments. In such situations, reevaluating previous results in light of new data is an essential exercise. We used three additional years of acoustic telemetry data to assess and update previous statistical models of survival of juvenile fall‐run Chinook Salmon Oncorhynchus tshawytscha smolts emigrating through the southern portion of the Sacramento–San Joaquin River Delta (hereafter, “Delta”) in California. Some previously identified relationships were maintained with the additional data, including the significance of water flow measures in areas outside the main‐stem migration route and the role of water temperature and river discharge into the system for upstream reaches. The net downstream‐directed discharge in the interior Delta was associated with fish movement to a large water pumping facility, but its perceived importance in the original analysis depended on a single dominant study year. Survival in dry years was predicted to be higher in the upstream region of the main‐stem San Joaquin River when a temporary rock barrier limited entry of fish and river flow to the first distributary encountered in the Delta. In normal and wet years, through‐Delta survival was predicted to be higher for fish that departed the main‐stem river at that distributary. However, considerable uncertainty remains in the modeling results. Additional monitoring will be necessary to further reduce uncertainty and ensure that the modeling results reflect the system as it responds to climate change.

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“…No single factor was identified as driving survival across all reaches of the Delta, but important drivers appeared to have reachspecific effects. For example, river discharge into the Delta was significantly correlated with survival in upstream reaches, whereas migratory route was more important for downstream reaches (Buchanan et al 2021).…”

Section: Factors Associated With Anadromymentioning

confidence: 99%

Counting the Parts to Understand the Whole: Rethinking Monitoring of Steelhead in California’s Central Valley

Eschenroeder¹,

Peterson²,

Hellmair³

et al. 2022

SFEWS

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Steelhead (Oncorhynchus mykiss expressing an anadromous life history) in the Sacramento and San Joaquin rivers and their tributaries in California’s Central Valley (CCV) belong to a Distinct Population Segment (DPS) that is listed as threatened under the US Endangered Species Act. Although contemporary management and recovery plans include numerous planned and ongoing efforts seeking to aid in DPS recovery—such as gravel augmentation, manipulation of spring flows, and restoration of rearing and spawning habitat—a paucity of data precludes the possibility of evaluating the effect of these actions on populations of Steelhead in CCV streams. Knowledge gaps relating to historic and current abundance, population-specific ratios of resident and anadromous life-history expression, and the influence of hatchery-reared fish remain largely unaddressed. This is partly a result of aspects of Steelhead biology that make them difficult to monitor, including the multitude of factors that contribute to the expression of anadromy, polymorphic populations, and migration periods that coincide with challenging field conditions. However, these gaps in understanding are also partly the result of an institutional focus on Chinook Salmon (Oncorhynchus tshawytscha) and a pervasive notion that actions benefiting Chinook populations will also benefit Steelhead populations. To evaluate these gaps and to suggest approaches for assessing DPS recovery actions, we review available data and existing monitoring efforts, and consider the actions necessary to inform the development of targeted O. mykiss monitoring programs. Current management and recovery goals focus on abundance estimates of Steelhead only, yet current monitoring is insufficient for reliable estimates. We argue that a reallocation of monitoring resources to better understand the interaction between resident O. mykiss and Steelhead would provide better data to estimate the vital rates needed to evaluate the effects of recovery actions.

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“…Anadromy on an Altered Landscape Buchanan et al (2021) found overall survival of Steelhead smolts through the Delta to be highly variable between and within years (6% to 69% from 2011 to 2016). No single factor was identified as driving survival across all reaches of the Delta, but important drivers appeared to have reachspecific effects.…”

Section: Factors Associated With Anadromymentioning

confidence: 99%

Counting the Parts to Understand the Whole: Rethinking Monitoring of Steelhead in California’s Central Valley

Eschenroeder¹,

Peterson²,

Hellmair³

et al. 2022

SFEWS

View full text Add to dashboard Cite

Steelhead (Oncorhynchus mykiss expressing an anadromous life history) in the Sacramento and San Joaquin rivers and their tributaries in California’s Central Valley (CCV) belong to a Distinct Population Segment (DPS) that is listed as threatened under the US Endangered Species Act. Although contemporary management and recovery plans include numerous planned and ongoing efforts seeking to aid in DPS recovery—such as gravel augmentation, manipulation of spring flows, and restoration of rearing and spawning habitat—a paucity of data precludes the possibility of evaluating the effect of these actions on populations of Steelhead in CCV streams. Knowledge gaps relating to historic and current abundance, population-specific ratios of resident and anadromous life-history expression, and the influence of hatchery-reared fish remain largely unaddressed. This is partly a result of aspects of Steelhead biology that make them difficult to monitor, including the multitude of factors that contribute to the expression of anadromy, polymorphic populations, and migration periods that coincide with challenging field conditions. However, these gaps in understanding are also partly the result of an institutional focus on Chinook Salmon (Oncorhynchus tshawytscha) and a pervasive notion that actions benefiting Chinook populations will also benefit Steelhead populations. To evaluate these gaps and to suggest approaches for assessing DPS recovery actions, we review available data and existing monitoring efforts, and consider the actions necessary to inform the development of targeted O. mykiss monitoring programs. Current management and recovery goals focus on abundance estimates of Steelhead only, yet current monitoring is insufficient for reliable estimates. We argue that a reallocation of monitoring resources to better understand the interaction between resident O. mykiss and Steelhead would provide better data to estimate the vital rates needed to evaluate the effects of recovery actions.

show abstract

Outmigration survival of a threatened steelhead population through a tidal estuary

Cited by 6 publications

References 44 publications

Understanding Salmon Migration Dynamics in a Data‐Limited Environment

Understanding Salmon Migration Dynamics in a Data‐Limited Environment

Counting the Parts to Understand the Whole: Rethinking Monitoring of Steelhead in California’s Central Valley

Counting the Parts to Understand the Whole: Rethinking Monitoring of Steelhead in California’s Central Valley

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