Abstract
Survival of juvenile salmonids in the Sacramento–San Joaquin Delta (Delta) varies by migration route, and thus the proportion of fish that use each route affects overall survival through the Delta. Understanding factors that drive routing at channel junctions along the Sacramento River is therefore critical to devising management strategies that maximize survival. Here, we examine entrainment of acoustically tagged juvenile Chinook Salmon into Sutter and Steamboat sloughs from the Sacramento River. Because these sloughs divert fish away from the downstream entrances of the Delta Cross Channel and Georgiana Slough (where fish access the low-survival region of the interior Delta), management actions to increase fish entrainment into Sutter and Steamboat sloughs are being investigated to increase through-Delta survival. Previous studies suggest that fish generally “go with the flow”—as net flow into a divergence increases, the proportion of fish that enter that divergence correspondingly increases. However, complex tidal hydrodynamics at sub-daily time-scales may be decoupled from net flow. Therefore, we modeled routing of acoustic tagged juvenile salmon as a function of tidally varying hydrodynamic data, which was collected using temporary gaging stations deployed between March and May of 2014. Our results indicate that discharge, the proportion of flow that entered the slough, and the rate of change of flow were good predictors of an individual’s probability of being entrained. In addition, interactions between discharge and the proportion of flow revealed a non-linear relationship between flow and entrainment probability. We found that the highest proportions of fish are likely to be entrained into Steamboat Slough and Sutter Slough on the ascending and descending limbs of the tidal cycle, when flow changes from positive to negative. Our findings characterize how patterns of entrainment vary with tidal flow fluctuations, providing information critical for understanding the potential effect of management actions (e.g., fish guidance structures) to modify routing probabilities at this location.
Highlights
IntroductionThe Sacramento–San Joaquin River Delta (hereafter referred to as “the Delta”) is a complex series of channels and embayments in west central California of the United States
The Sacramento–San Joaquin River Delta is a complex series of channels and embayments in west central California of the United States
Fish that migrate through Steamboat and Sutter sloughs exhibit survival similar to fish that remain in the Sacramento River at high flows but have lower survival at low flows (Perry et al 2018)
Summary
The Sacramento–San Joaquin River Delta (hereafter referred to as “the Delta”) is a complex series of channels and embayments in west central California of the United States. The physical complexity of the Delta poses significant challenges for understanding how juvenile salmon negotiate the complex channel network and survive in different migration routes. Such information is critical for understanding how water-management actions, such as operation of water diversions, influence survival of juvenile salmon. Fish that migrate through Steamboat and Sutter sloughs exhibit survival similar to fish that remain in the Sacramento River at high flows but have lower survival at low flows (Perry et al 2018)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
