Pacific Salmon Prespawn Mortality: Patterns, Methods, and Study Design Considerations

Bowerman, Tracy; Keefer, Matthew L.; Caudill, Christopher C.

doi:10.1080/03632415.2016.1245993

Cited by 48 publications

(72 citation statements)

References 33 publications

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“…This depletion rate suggests that energetic status is more predictive of mortality for adults returning after years with poor ocean productivity (Crossin et al 2004;Todd et al 2008) or for adults that encounter very warm migration conditions and therefore more rapidly exhaust reserves (Hinch and Rand 2000;Rand et al 2006). The energy-mortality relationship in spring-run Chinook Salmon also may be less likely to manifest during migration than during the often extended (weeks to months) prespawn holding period for this adult life history type (Hearsey and Kinziger 2015;Bowerman et al 2016) We did not find mortality differences between hatchery and wild salmon or between sexes. Similar survival for the two origin groups probably reflected the limited fisheries harvest in the Willamette River main stem.…”

Section: Mortality Hypothesesmentioning

confidence: 79%

Condition‐Dependent En Route Migration Mortality of Adult Chinook Salmon in the Willamette River Main Stem

Keefer

Jepson

Naughton

et al. 2017

N American J Fish Manag

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Episodically high adult mortality during migration and near spawning sites has hindered the recovery of threatened spring‐run Chinook Salmon Oncorhynchus tshawytscha in Oregon's Willamette River basin. In 2011–2014, we assessed migration mortality for 762 radio‐tagged adults along a ~260‐km reach of the main stem of the Willamette River. Annual survival of salmon to spawning tributaries ranged from 0.791 (95% CI = 0.741–0.833) to 0.896 (0.856–0.926), confirming concerns about mortality in the migration corridor. In a series of general linear models, descaling, marine mammal injuries, and head injuries to adult Chinook Salmon were linked to reduced survival during migration to tributaries. Many injuries were minor (i.e., epidermal abrasions), which we hypothesize were unlikely to have caused direct mortality but may have increased salmon vulnerability to pathogens or other disease processes. Mortality in the main stem was not significantly associated with salmon body size, energetic status, sex, origin (hatchery, wild), river discharge, or water temperature metrics. The ~10–21% estimates of en route mortality in this study provide an important benchmark for the main stem of the Willamette River. The estimates complement ongoing efforts to quantify mortality of adult Chinook Salmon in Willamette River tributaries and after collection and transport to spawning sites above high‐head hydroelectric dams. Received September 15, 2016; accepted December 1, 2016 Published online March 3, 2017

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Section: Mortality Hypothesesmentioning

confidence: 79%

Condition‐Dependent En Route Migration Mortality of Adult Chinook Salmon in the Willamette River Main Stem

Keefer

Jepson

Naughton

et al. 2017

N American J Fish Manag

Self Cite

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“…; Bowerman et al. ). Within the Willamette River basin, considerable variation in PSM rates has been reported among locations and among years at a single location (Sharpe et al.…”

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confidence: 97%

Prespawn Mortality of Female Chinook Salmon Increases with Water Temperature and Percent Hatchery Origin

et al. 2018

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High rates of prespawn mortality, when adult salmon die after completing migration but prior to spawning, can lead to population declines and can impede recovery of threatened stocks. In this study, annual prespawn mortality of female Chinook Salmon Oncorhynchus tshawytscha ranged from 1% to 100% over 14 years in seven study reaches located throughout the upper Willamette River basin, Oregon. Prespawn mortality rates were positively correlated with the annual maximum 7‐d average maximum stream temperature and the percentage of spawning fish of hatchery origin. Observed prespawn mortality rates varied considerably, but annual female prespawn rates were consistently >80% where maximum temperatures exceeded 20°C and the composition of spawning fish was >80% hatchery origin. In several spawning tributaries, prespawn mortality rates generally decreased at higher elevations. The proximate cause of prespawn death was not evaluated here, and observed patterns likely reflected additional factors that influence mortality either directly or indirectly, such as handling, dam passage, fishing pressure, instream habitat, energetic budget, fish density, and pathogen loads.

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“…; Bowerman et al. ), although no systematic analysis has been conducted to determine whether these events are increasing relative to historical averages.…”

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confidence: 99%

Global Warming of Salmon and Trout Rivers in the Northwestern U.S.: Road to Ruin or Path Through Purgatory?

et al. 2018

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Large rivers constitute small portions of drainage networks but provide important migratory habitats and fisheries for salmon and trout when and where temperatures are sufficiently cold. Management and conservation of coldwater fishes in the current era of rapid climate change require knowing how riverine thermal environments are evolving and the potential for detrimental biological impacts. Robust estimates of warming rates, however, are lacking due to limited long‐term temperature monitoring, so we compiled the best available multidecadal records and estimated trends at 391 sites in the 56,500‐km river network of the northwestern USA. Warming trends were prevalent during summer and early fall months in recent 20‐ and 40‐year periods (0.18–0.35°C per decade during 1996–2015 and 0.14–0.27°C per decade during 1976–2015), paralleled air temperature trends, and were mediated by discharge trends at regional and local levels. To illustrate the biological consequences of warming later in this century, trend estimates were used to inform selection of river temperature scenarios and assess changes in thermal exposure of adult Sockeye Salmon Oncorhynchus nerka migrating to four population areas as well as thermal habitat shifts for resident Brown Trout Salmo trutta and Rainbow Trout O. mykiss populations throughout the region. Future warming of 1–3°C would increase Sockeye Salmon exposure by 5–16% (3–143 degree‐days) and reduce thermally suitable riverine trout habitats by 8–31% while causing their upstream shift. Effects of those changes on population persistence and fisheries are likely to be context dependent, and strategic habitat restoration or adaptation strategies could ameliorate some biological impairments, but effectiveness will be tempered by the size of rivers, high costs, and pervasiveness of thermal effects. Most salmon and trout rivers will continue to provide suitable habitats for the foreseeable future, but it also appears inevitable that some river reaches will gradually become too warm to provide traditional habitats.

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Pacific Salmon Prespawn Mortality: Patterns, Methods, and Study Design Considerations

Cited by 48 publications

References 33 publications

Condition‐Dependent En Route Migration Mortality of Adult Chinook Salmon in the Willamette River Main Stem

Condition‐Dependent En Route Migration Mortality of Adult Chinook Salmon in the Willamette River Main Stem

Prespawn Mortality of Female Chinook Salmon Increases with Water Temperature and Percent Hatchery Origin

Global Warming of Salmon and Trout Rivers in the Northwestern U.S.: Road to Ruin or Path Through Purgatory?

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