Development of underwater recorders to quantify predation of juvenile Chinook salmon (Oncorhynchus tshawytscha) in a river environment

Demetras, Nicholas J.; Huff, David D.; Michel, C.; Smith, Joseph M.; Cutter, George R.; Hayes, Sean A.; Lindley, Steven T.

doi:10.7755/fb.114.2.5

Cited by 14 publications

(25 citation statements)

References 6 publications

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“…Specifically, PERs tend to measure predation rates in the channel of the river and do not operate as effectively in shallow‐water environments (<1 m) and the associated submerged aquatic vegetation typically found there (Demetras et al. ). In addition, fish density acoustic surveys conducted by Cutter et al.…”

Section: Discussionmentioning

confidence: 99%

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Limitations of Active Removal to Manage Predatory Fish Populations

Michel

Smith

Lehman

et al. 2020

N American J Fish Manag

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Programs to control predatory fishes have successfully increased the survival of imperiled prey fishes in some cases, but efficacy depends on the population dynamics and ecological interactions between the predators, prey, and the rest of the community. In California's Sacramento–San Joaquin Delta, extremely low survival of downstream‐migrating juvenile salmonids has been ascribed in part to predation by abundant nonnative fishes that have become naturalized in the system. This study aimed to determine the effectiveness of removing some of these predatory fish to increase the survival of juvenile salmonids in the San Joaquin River. In 2014 and 2015, we used predation event recorders (PERs) to estimate predation rates before and after localized, experimental predatory fish removals and additions. We also estimated survival of juvenile Chinook Salmon Oncorhynchus tshawytscha before and after predator manipulations in 2014 using acoustic tags. We found no statistically significant evidence for an effect of predator removals or additions on survival rates of Chinook Salmon (as measured by acoustic tags) or on predation rates (as measured by PERs), despite a one‐time reduction of approximately 40–70% of all predators from “removal” sites and relocation to “addition” sites. We review examples of successful predator control programs elsewhere, highlighting key differences between those programs and our study in the Sacramento–San Joaquin Delta.

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Section: Discussionmentioning

confidence: 99%

“…The PERs, which were described in detail by Demetras et al. (), were drifting buoys with a live Chinook Salmon smolt attached as bait. Each PER contained a GPS tracker and a predation‐triggered timer that recorded the exact time and location of the predation event.…”

Section: Methodsmentioning

confidence: 99%

Limitations of Active Removal to Manage Predatory Fish Populations

Michel

Smith

Lehman

et al. 2020

N American J Fish Manag

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“…Very recent published work by Sabal et al (2016) and Demetras et al (2016) indicate that Striped Bass predation upon juvenile Chinook Salmon could be substantial, although the amount of predation experienced by wild as opposed to hatchery fish-or those in habitats other than predation hot spotsremains unknown. In a multi-faceted study, Sabal et al (2016) (Davis et al 2012).…”

Section: Predation Studies On Delta Fishesmentioning

confidence: 99%

“…Several recent studies address the predation issue directly, most notably Cavallo et al (2012), Sabal et al (2016) and Demetras et al (2016). In an ambitious study, Cavallo et al (2012), attempted a BACI (Before, After, Control, Intervention) assessment of how predatory fishes affected Chinook salmon juvenile survival, using boat electrofishing to remove predatory fishes from a section of the Mokelumne River.…”

Section: Predation Studies On Delta Fishesmentioning

confidence: 99%

“…In predation hot spots in the Delta, predators may aggregate and consume large numbers of prey that are disoriented by: (1) unnatural or reversed flow patterns, and (2) modified habitat structures such as fish ladders, water abstraction devices, modified channels, or impoundments (Davis et al 2012;Grossman et al 2013). Demetras et al (2016) developed an innovative predator detection system that documented predation by Striped Bass and unidentified fish predators on tethered Chinook Salmon, and found a positive relationship between current velocity and predation rate and an inverse relationship between water column depth and predation rate. Although this highly innovative system documented predation by Striped Bass and other predators on tethered Chinook Salmon, it is difficult to extrapolate these results to estimates of predation rates throughout the Delta.…”

Section: Predation Studies On Delta Fishesmentioning

confidence: 99%

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Predation on Fishes in the Sacramento-San Joaquin Delta: Current Knowledge and Future Directions

Grossman¹

2016

SFEWS

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Warm, dry winters truncate timing and size distribution of seaward‐migrating salmon across a large, regulated watershed

Munsch

Greene

Johnson

et al. 2019

Ecological Applications

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Ecologists are pressed to understand how climate constrains the timings of annual biological events (phenology). Climate influences on phenology are likely significant in estuarine watersheds because many watersheds provide seasonal fish nurseries where juvenile presence is synched with favorable conditions. While ecologists have long recognized that estuaries are generally important to juvenile fish, we incompletely understand the specific ecosystem dynamics that contribute to their nursery habitat value, limiting our ability to identify and protect vital habitat components. Here we examined the annual timing of juvenile coldwater fish migrating through a seasonally warm, hydrologically managed watershed. Our goal was to (1) understand how climate constrained the seasonal timing of water conditions necessary for juvenile fish to use nursery habitats and (2) inform management decisions about (a) mitigating climate‐mediated stress on nursery habitat function and (b) conserving heat‐constrained species in warming environments. Cool, wet winters deposited snow and cold water into mountains and reservoirs, which kept the lower watershed adequately cool for juveniles through the spring despite the region approaching its hot, dry summers. For every 1°C waters in April were colder, the juvenile fish population (1) inhabited the watershed 4–7 d longer and (2) entered marine waters, where survival is size selective, at maximum sizes 2.1 mm larger. Climate therefore appeared to constrain the nursery functions of this system by determining seasonal windows of tolerable rearing conditions, and cold water appeared to be a vital ecosystem component that promoted juvenile rearing. Fish in this system inhabit the southernmost extent of their range and already rear during the coolest part of the year, suggesting that a warming climate will truncate rather than shift their annual presence. Our findings are concerning for coldwater diadromous species in general because warming climates may constrain watershed use and diminish viability of life histories (e.g., late springtime rearing) and associated portfolio benefits over the long term. Lower watershed nurseries for coldwater fish in warming climates may be enhanced through allocating coldwater reservoir releases to prolong juvenile rearing periods downstream or restorations that facilitate colder conditions.

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Development of underwater recorders to quantify predation of juvenile Chinook salmon (Oncorhynchus tshawytscha) in a river environment

Cited by 14 publications

References 6 publications

Limitations of Active Removal to Manage Predatory Fish Populations

Limitations of Active Removal to Manage Predatory Fish Populations

Predation on Fishes in the Sacramento-San Joaquin Delta: Current Knowledge and Future Directions

Warm, dry winters truncate timing and size distribution of seaward‐migrating salmon across a large, regulated watershed

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