Detrital food web contributes to aquatic ecosystem productivity and rapid salmon growth in a managed floodplain

Jeffres, Carson A.; Holmes, Eric; Sommer, Ted; Katz, Jacob V. E.

doi:10.1371/journal.pone.0216019

Cited by 41 publications

(60 citation statements)

References 37 publications

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“…Inundation duration of several weeks (typically 3–6 weeks) facilitates the development of highly productive invertebrate food webs and improved foraging opportunities for fish [ 28 ]. Chinook Salmon reared in floodplain and off-channel habitats experience more rapid growth rates compared to those rearing in adjacent leveed river channels rivers due to more abundant invertebrate prey [ 24 , 29 ]. For anadromous salmonid species such as Chinook Salmon improved growth during the freshwater juvenile stage is correlated with larger size at ocean entry and increased survivorship to adulthood [ 30 – 33 ].…”

Section: Introductionmentioning

confidence: 99%

“…For anadromous salmonid species such as Chinook Salmon improved growth during the freshwater juvenile stage is correlated with larger size at ocean entry and increased survivorship to adulthood [ 30 – 33 ]. While the potential benefits to juvenile Chinook Salmon rearing on flooded bypasses is well established [ 24 , 26 , 27 , 29 ], there is little published research testing methodologies for establishing the optimal physical and biological conditions to achieve maximal benefit on these managed floodplains.…”

Section: Introductionmentioning

confidence: 99%

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Reconciling fish and farms: Methods for managing California rice fields as salmon habitat

et al. 2021

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Rearing habitat for juvenile Chinook Salmon (Oncorhynchus tshawytscha) in California, the southernmost portion of their range, has drastically declined throughout the past century. Recently, through cooperative agreements with diverse stakeholders, winter-flooded agricultural rice fields in California’s Central Valley have emerged as ecologically functioning floodplain rearing habitat for juvenile Chinook Salmon. From 2013 to 2016, we conducted a series of experiments examining methods to enhance habitat benefits for fall-run Chinook Salmon reared on winter-flooded rice fields in the Yolo Bypass, a modified floodplain managed for flood control, agriculture, and wildlife habitat in the Sacramento River Valley of California. Investigations included studying the effect of 1) post-harvest field substrate; 2) depth refugia; 3) duration of field drainage; and 4) duration of rearing occupancy on in-situ diet, growth and survival of juvenile salmon. Post-harvest substrate treatment had only a small effect on the lower trophic food web and an insignificant effect on growth rates or survival of rearing hatchery-origin, fall-run Chinook Salmon. Similarly, depth refugia, created by trenches dug to various depths, also had an insignificant effect on survival. Rapid field drainage yielded significantly higher survival compared to drainage methods drawn out over longer periods. A mortality of approximately one third was observed in the first week after fish were released in the floodplain. This initial mortality event was followed by high, stable survival rates for the remainder of the 6-week duration of floodplain rearing study. Across years, in-field survival ranged 7.4–61.6% and increased over the course of the experiments. Despite coinciding with the most extreme drought in California’s recorded history, which elevated water temperatures and reduced the regional extent of adjacent flooded habitats which concentrated avian predators, the adaptive research framework enabled incremental improvements in design to increase survival. Zooplankton (fish food) in the winter-flooded rice fields were 53-150x more abundant than those sampled concurrently in the adjacent Sacramento River channel. Correspondingly, observed somatic growth rates of juvenile hatchery-sourced fall-run Chinook Salmon stocked in rice fields were two to five times greater than concurrently and previously observed growth rates in the adjacent Sacramento River. The abundance of food resources and exceptionally high growth rates observed during these experiments illustrate the potential benefits of using existing agricultural infrastructure to approximate the floodplain wetland physical conditions and hydrologic patterns (shallow, long-duration inundation of cool floodplain habitats in mid-winter) under which Chinook Salmon evolved and to which they are adapted.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Reconciling fish and farms: Methods for managing California rice fields as salmon habitat

et al. 2021

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“…Cross section of juvenile Chinook salmon weekly lens growth on the Yolo Bypass. Time 0 represents fish from the hatchery arriving to the floodplain enclosure experiment detailed in Jeffres et al (2020), then 16, 22, 29 and 36 days on the floodplain…”

Section: Resultsmentioning

confidence: 99%

“…The assimilation rate in these lenses was similar to Granneman et al (2018), yet muscle assimilation rate was faster than previously seen in laboratory studies (Heady & Moore, 2013). This is likely due to rapid growth rates occurring on the floodplain for these fish (Jeffres et al, 2020). Nevertheless, better methods to understand frequency and mechanisms of layer formulation would be valuable to strengthen our understanding of the temporal resolution of eye lenses for diet reconstructions in salmon and other species.…”

Section: Discussionmentioning

confidence: 99%

“…We build on the landscape‐scale experimental floodplain ecology research outlined in Jeffres et al (2020) to include a dietary reconstruction component using isotopes. Briefly, hatchery‐origin juvenile Chinook Salmon were released within experimental managed floodplain fields in 2016 and captured weekly with some retained to characterize the isotopic baseline for the hatchery (Figure 1; Table 1).…”

Section: Methodsmentioning

confidence: 99%

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Advancing diet reconstruction in fish eye lenses

et al. 2021

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Tracking habitat use and dietary shifts in migratory species is vital to conservation and management. Yet, conventional animal tracking often precludes tracking small juveniles at critical life stages where recruitment bottlenecks often manifest. Stable isotope analysis (SIA) in consecutive laminae in eye lenses, a protein‐rich depositional tissue, has emerged as a promising tool in fishes to develop long‐term interpretive records of dietary histories using a single archival tissue. Currently, studies using fish eye lenses to study SIA in diets have primarily been conducted in marine environments using δ13C and δ15N to identify resource partitioning, ontogenetic shifts and lifelong trophic histories. To date, no studies have examined freshwater taxa nor used δ34S isotopes. We placed juvenile (Chinook Salmon) Oncorhynchus tshawytscha in experimental enclosures in three different freshwater habitats (hatchery, river and seasonal floodplain), each with isotopically distinct and well‐characterized food webs. This experimental approach allowed us to directly measure diets and quantify tissue turnover rates in eye lenses as well as the isotopic fractionation among fish tissues (fin and muscle tissue) in distinct habitat types using stable isotopes δ13C, δ15N and δ34S. Bulk eye‐lens stable isotope measurements were analysed for juvenile salmon lenses and were found to be consistent with the isotopic values of rearing habitats. Slight additional isotopic fractionation was only found in δ13C. We then successfully applied the method to a larger, reproductively mature adult salmon captured in freshwater and inferred juvenile habitat use. SIA in eye lenses using three dietary isotopes (δ13C, δ15N and δ34S) has significant potential for answering critical questions about migration, diet, foraging ecology and life history of migratory aquatic animals on Earth. Such information would have immediate application towards conservation management of diverse species and habitats at multiple scales.

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Behavioral cues enable native fishes to exit a California floodplain while leaving non‐native fishes behind

et al. 2022

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Floodplains are highly productive environments that provide critical rearing habitat and increased growth for diverse native fishes, including juvenile Chinook salmon (Oncorhynchus tshawytscha). Yet, stranding during the flood recession is a potential negative outcome in restored ecosystems where environmental cues are not always present as they were under historical conditions. Outmigration cues of native and non‐native fishes from a restored floodplain were evaluated along the Cosumnes River, CA, USA. This river is the only remaining major unregulated river in the Sierra Nevada that flows into the Central Valley. It remains unclear how native and non‐native fishes utilize spatiotemporally heterogeneous habitats in the Cosumnes River; however, a better understanding of these dynamics could yield insight into how degraded river ecosystems in the region could be rehabilitated to benefit native fishes. In 2018 and 2019, daily fyke net surveys of fish assemblages were conducted within the floodplain and in outmigration corridors, along with the collection of environmental data to identify possible cues. Bayesian modeling showed that temperature increases, along with the rate of floodplain drawdown and the average flow over a rolling seven‐day period, were important triggers for cuing native fishes to exit the floodplain. We conclude that the numerous benefits to the aquatic food web and growth of native fishes justify the risk of stranding that floodplain restoration poses, particularly when supplemented with outmigration cues.

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Detrital food web contributes to aquatic ecosystem productivity and rapid salmon growth in a managed floodplain

Cited by 41 publications

References 37 publications

Reconciling fish and farms: Methods for managing California rice fields as salmon habitat

Reconciling fish and farms: Methods for managing California rice fields as salmon habitat

Advancing diet reconstruction in fish eye lenses

Behavioral cues enable native fishes to exit a California floodplain while leaving non‐native fishes behind

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