Evidence of prevalent heat stress in Yukon River Chinook salmon

Biela, Vanessa R. von; Bowen, Lizabeth; McCormick, Stephen D.; Carey, Michael P.; Donnelly, Daniel S.; Waters, Shannon; Regish, Amy M.; Laske, Sarah M.; Brown, Randy J.; Larson, Sean; Zuray, Stanley; Zimmerman, Christian E.

doi:10.1139/cjfas-2020-0209

Cited by 21 publications

(28 citation statements)

References 78 publications

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“…Observations reported here are part of an emerging picture that biological tipping points are being reached for Alaska’s Pacific salmon, where warming switches from beneficial to detrimental in some locations, years, and life stages. In western Alaska, evidence of heat stress was detected in about half of spawning Yukon River Chinook Salmon sampled during 2016 and 2017, when migration water temperatures exceed 18°C (von Biela et al 2020). Jones et al (2020), in a south‐central Alaska study, also documented the negative effects of water temperatures above 18°C on annual measures of Chinook Salmon production.…”

Section: Discussionmentioning

confidence: 99%

“…Illustrations along the bottom depict Pacific salmon spawning outcomes under three different conditions. Left panel shows how prolonged, high water temperatures causes heat stress mortality of Pacific salmon when the upper thermal limit reached the Yukon River (water temperatures from Alaska Department of Fish and Game and discharge data from U.S. Geological Survey [USGS] gage station 15565447, Pilot Station; dashed line is 18°C water temperature threshold associated with heat stress from von Biela et al 2020). Center panel shows representative PWS rain‐driven stream where thousands of Pink Salmon carcasses were observed (water temperature and discharge data from USGS gage station 15215900, Glacier River, Cordova, glaciers actually outside this watershed).…”

Section: Discussionmentioning

confidence: 99%

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Premature Mortality Observations among Alaska’s Pacific Salmon During Record Heat and Drought in 2019

et al. 2022

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Widespread mortality of Pacific salmon Oncorhynchus spp. returning to spawn in Alaska coincided with record‐breaking air temperatures and prolonged drought in summer 2019. Extreme environmental conditions are expected to happen more frequently with rapid climate change and challenge the notion that Alaska could indefinitely provide abundant, cool freshwater habitat for Pacific salmon. A total of 110 geographically widespread opportunistic observations of premature mortality (carcasses) were collected from a variety of sources. Premature mortalities were documented for Pink Salmon Oncorhynchus gorbuscha, Sockeye Salmon O. nerka, Chum Salmon O. keta, Chinook Salmon O. tshawytscha, and Coho Salmon O. kisutch. Additionally, observations of Pink Salmon returning to spawn in Prince William Sound streams in 2019, obtained from systematic aerial surveys conducted annually, revealed low migration success in 87% of rain‐driven streams (n = 30), 52% of snow‐driven streams (n = 65), and only 18% of glacier‐driven streams (n = 11). Salmon mortality observations were consistent with death due to heat stress resulting from high water temperatures or drought caused hypoxia and stranding. Developing a better understanding of how broad‐scale climate patterns manifest at the stream scale can help us determine whether a major shift in Pacific salmon productivity is underway and inform fisheries management plans to better mitigate future risks.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Premature Mortality Observations among Alaska’s Pacific Salmon During Record Heat and Drought in 2019

et al. 2022

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“…There are many populations of sockeye salmon in northern British Columbia and Alaska that are not in large decline (Ruggerone and Irvine 2018) as so many are in southern British Columbia (Hyatt et al 2017) although there is good evidence of reductions in mature size and changes to age structure in many of these northern populations (Oke et al 2020) indicating strong effects of climate change and increased competition. Trends in sex ratios and information on female mortality should be incorporated into assessment and research on these northern populations particularly as several of them are now experiencing summer high water temperatures causing migration mortality (von Biela et al 2020). We encourage research into how global change could be affecting sex-specific mortality in other fish species and regions, and in particular, advocate for a more thorough understanding of the physiological underpinnings of high female mortality.…”

Section: Conservation and Management Implicationsmentioning

confidence: 99%

Exceptionally high mortality of adult female salmon: a large-scale pattern and a conservation concern

Hinch

Bett

Eliason

et al. 2021

Can. J. Fish. Aquat. Sci.

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In recent decades, the relative proportion of female sockeye salmon (Oncorhynchus nerka) on spawning grounds of several British Columbia populations has declined. Coincident with the decline has been large changes to oceanic, estuarine and river migration environments. Over the past 30 years, numerous telemetry tracking and laboratory studies have examined mortality of adult Fraser River sockeye salmon during ocean and freshwater migrations. We reviewed 19 studies that provided 40 situations where male and female mortality could be directly compared. Female mortality averaged 2.1 times greater than males, and up to 8-fold higher. High female mortality was also evident in migrating coho salmon (O. kisutch) and Chinook salmon (O. tshawytscha), and for sockeye salmon in other systems. Female mortality was highest when migration conditions were challenging (e.g. high / turbulent flows, high temperatures, confinement, or handling), and towards end of river migration. We review mechanisms for differential mortality, including energy exhaustion, cardiac performance, physiological stress, and immune factors. Female-specific mortality will become even more pronounced in coming years as ocean and riverine conditions continue to change.

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“…For instance, the lower Yukon River was abnormally warm during the migration in 2019 and water levels throughout the river were well below historic averages (ADFG, 2019). This warm water was linked to stress and pre‐spawn mortality in O. tshawytscha in the lower river (discussed in von Biela et al ., 2020) and it is possible there were latent effects on those salmon in the upper Yukon River. In 2020, water temperatures were cooler and water levels were well above historic averages (ADFG, 2020).…”

Section: Discussionmentioning

confidence: 99%

High egg retention in Chinook Salmon Oncorhynchus tshawytscha carcasses sampled downstream of a migratory barrier

Twardek

Lapointe

Cooke

2022

Journal of Fish Biology

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Barriers in rivers have the potential to severely decrease functional connectivity between habitats. Failure to pass barriers and reach natal spawning habitat may compromise individual reproductive success, particularly for semelparous, philopatric species that rely on free‐flowing rivers to reach natal habitat during their once‐in‐a‐lifetime spawning migrations. To investigate the consequences of in‐river barriers on fish spawning success, we quantified egg retention and spawning effort (caudal fin wear) in female Chinook Salmon Oncorhynchus tshawytscha carcasses collected downstream of the Whitehorse Hydro Plant on the upper Yukon River and at a nearby free‐flowing tributary (Teslin River) from 2018 to 2020 (~2900 km migrations). Previous studies have demonstrated that a large proportion of fish attempting to reach spawning locations upstream of the hydro plant fail to pass the associated fishway. We estimated nearly all female salmon failing to pass the hydro plant attempted spawning in non‐natal habitat downstream, but that these females retained ~34% of their total fecundity compared to ~6% in females from the free‐flowing river. Females downstream of the hydro plant also had lower wear on their caudal fin, a characteristic that was correlated with increased egg deposition. Egg retention did not vary across years with different run sizes, and we propose that egg retention downstream of the hydro plant was not driven by density‐dependent mechanisms. Findings from this work indicate that female Chinook Salmon can still deposit eggs following failed fish passage and failure to reach natal spawning sites, though egg retention rates are considerably higher and uncertainties remain about reproductive success. We encourage researchers to incorporate carcass surveys into fish passage evaluations for semelparous species to fully account for consequences of failed passage.

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Evidence of prevalent heat stress in Yukon River Chinook salmon

Cited by 21 publications

References 78 publications

Premature Mortality Observations among Alaska’s Pacific Salmon During Record Heat and Drought in 2019

Premature Mortality Observations among Alaska’s Pacific Salmon During Record Heat and Drought in 2019

Exceptionally high mortality of adult female salmon: a large-scale pattern and a conservation concern

High egg retention in Chinook Salmon Oncorhynchus tshawytscha carcasses sampled downstream of a migratory barrier

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