Lower Snake Research Articles

Limitations of invasive snake control tools in the context of a new invasion on an island with abundant prey

In October 2020, a new population of invasive brown treesnakes (Boiga irregularis) was discovered on the 33-ha Cocos Island, 2.5 km off the south coast of Guam. Cocos Island is a unique conservation resource, providing refuge for many lizards and birds, including endangered species, which were extirpated from mainland Guam by invasive predators including brown treesnakes. We sought to evaluate the usefulness of toxic baiting with acetaminophen-treated carrion baits and cage trapping, common tools for the control of brown treesnakes on mainland Guam, as potential eradication tools on Cocos Island. We evaluated multiple bait types and bait presentations: on the ground, suspended in the canopy emulating aerial bait applications and in four plastic-tube bait station configurations intended to exclude non-target species. We monitored all baits with time-lapse cameras. Despite improved exclusion of non-targets by bait station design, most baits were quickly removed by non-target species, particularly coconut crabs (Birgus latro) and Mariana monitors (Varanus tsukamotoi). Monitoring of 1,250 baits available for 2,427 bait nights resulted in no observations of brown treesnakes taking any bait. Subsequently, we tested two trap types commonly used on Guam and compared trapping success with live versus dead mouse lures. In 10,553 trap nights using live and dead mouse lures, we only captured one brown treesnake, in a trap with a live mouse lure. These baiting and trapping rates are so low as to be ineffectual for all practical purposes. Concurrent visual searching and hand capture of brown treesnakes during initial rapid response efforts demonstrates that these low baiting and trapping success rates are not a result of low snake density. We make a case for our assumption that the ineffectiveness of these tools on Cocos Island is due to the context of extremely high abundance of preferred live prey, primarily large geckos and birds. Our results have profound conservation ramifications, because any future island invasions by brown treesnakes are likely to occur within similarly prey-rich environments where these baiting and trapping methods might be similarly ineffective.

Factors affecting powerhouse passage of spring migrant smolts at federally operated hydroelectric dams of the Snake and Columbia rivers

From 2008 to 2018, acoustic telemetry studies were conducted to evaluate dam passage survival of spring migrant Chinook salmon and steelhead smolts at seven of the eight federally operated dams on the lower Snake and Columbia rivers. Data from over 87 000 dam passage events were evaluated using regression modeling to identify the effect of spill operations, environmental conditions, and fish characteristics on powerhouse passage probability. In general, powerhouse passage was positively correlated with discharge, negatively correlated with forebay temperature and fish size, and higher for fish that passed the dam at night and for those that approached from the powerhouse side of the river, suggesting powerhouse passage is largely a function of smolt activity level and swimming ability. As such, spilling large volumes of water to reduce powerhouse passage is likely to be most effective during times of reduced activity and swimming ability (e.g., at night, high flows, and cold temperatures). This information can be used to develop dam- and time-specific spill operations that optimize smolt passage, power generation, and other competing demands, such as adult passage.

Hydropower peaking and stalled salmon migration are linked by altered reservoir hydraulics: A multidisciplinary synthesis and hypothesis

AbstractAdding variable renewable energy (solar, wind) in electricity portfolios will increase need for fast grid responses through hydropower peaking. Over 60 years of daily hydropeaking by four dams on the lower Snake River, United States of America provide an example of long‐term environmental impacts. Downstream‐migrating Chinook salmon (Oncorhynchus tshawytscha) subyearlings that normally transit the dammed river in summer slowed their migration into autumn with about one‐third of those delayed overwintering in the reservoirs. Specific cause for stalled migration is controversial, with options including evolution of a new migratory strain and action of environment on individual migrants. Analysis of archived dam data shows evidence of reservoir seiches (standing waves of waterbody oscillations) caused by within‐day hydropower peaking during the October–February period of stalled migration. Analyses of limnological literature identified typical water movements in seiches and analyses of biological literature identified typical effects on fish kinematics (shape, motion) of changing flows in a fish's immediate proximity. Process‐focused inference predicts anomalous fish‐migration behavior in seiche hydraulics, which matches fish‐tracking data obtained by others in Lower Monumental Reservoir. Fish tracks include upstream swimming (‘downstream’ in reverse seiche flows) and periods of disoriented movements typical of responses to repeatedly changing flows. This multi‐disciplinary, process‐focused synthesis yields a testable hypothesis that seiche‐flow hydraulics in the lower Snake River reservoirs from hydropower peaking contribute to known out‐migration delay and overwintering of late‐migrating fall Chinook salmon subyearlings. As hydropower peaking causes seiches in downstream reservoirs elsewhere in North America and Europe, migratory species elsewhere may be susceptible to similar migration delays with long‐term population effects.

Statement of the American Fisheries Society and the Western Division of AFS About the Need to Breach the Four Dams on the Lower Snake River

FisheriesEarly View AFS News Statement of the American Fisheries Society and the Western Division of AFS About the Need to Breach the Four Dams on the Lower Snake River Drue Banta Winters, Corresponding Author Drue Banta Winters AFS Science Communication and Government Affairs Consultant. [email protected] Search for more papers by this author Drue Banta Winters, Corresponding Author Drue Banta Winters AFS Science Communication and Government Affairs Consultant. [email protected] Search for more papers by this author First published: 06 March 2023 https://doi.org/10.1002/fsh.10906Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Early ViewOnline Version of Record before inclusion in an issue RelatedInformation

Improving Abundance Estimates of Spring–Summer Snake River Chinook Salmon for Fisheries Management

AbstractThe Columbia River basin is home to a run of spring–summer Chinook Salmon Oncorhynchus tshawytscha that returns to the Snake River drainage of Idaho, Oregon, and Washington in the Pacific Northwest. Historically, the run was one of the more productive throughout the Columbia River basin. However, Snake River spring–summer Chinook Salmon have experienced declines in abundance due to overfishing, habitat degradation, and dams. Several stocks are listed as threatened under the U.S. Endangered Species Act and are supported by mitigation hatcheries funded by Idaho Power Company, the Lower Snake River Compensation Plan, and the Bonneville Power Administration. To maximize tribal and state harvest of returning hatchery adults, minimize impacts on wild fish, and ensure that enough hatchery fish return to meet broodstock needs, careful fisheries management is required. Since 2008, managers have used hatchery adults, PIT‐tagged as juveniles and detected at Lower Granite Dam, to generate adult abundance estimates. In season, these estimates inform state and tribal harvest shares and ensure that broodstock needs are met. Postseason, they provide smolt‐to‐adult survival and return rates. Since 2012, parentage‐based tagging (PBT) has provided an alternative method to estimate stock‐ and age‐specific returns at Lower Granite Dam, since returning hatchery adults sampled at Lower Granite Dam can be assigned to their parents. We compared stock‐specific abundance estimates between PIT‐ and PBT‐derived methodologies for return years 2016–2019. Across all years, PIT tag estimates accounted for 65% of the PBT‐based estimates at Lower Granite Dam across all age‐groups and release sites combined. This underrepresentation across all groups equated to 49,833 fish that were not accounted for in PIT tag abundance estimates. It is clear that PBT‐based estimates should aide in‐season harvest management and postseason run reconstruction to avoid the known bias of estimates from PIT tags, especially during years of low returns when increased accuracy is critical.

Cumulative effects of piscivorous colonial waterbirds on juvenile salmonids: A multi predator-prey species evaluation.

We investigated the cumulative effects of predation by piscivorous colonial waterbirds on the survival of multiple salmonid (Oncorhynchus spp.) populations listed under the U.S. Endangered Species Act (ESA) and determined what proportion of all sources of fish mortality (1 –survival) were due to birds in the Columbia River basin, USA. Anadromous juvenile salmonids (smolts) were exposed to predation by Caspian terns (Hydroprogne caspia), double-crested cormorants (Nannopterum auritum), California gulls (Larus californicus), and ring-billed gulls (L. delawarensis), birds known to consume both live and dead fish. Avian consumption and survival probabilities (proportion of available fish consumed or alive) were estimated for steelhead trout (O. mykiss), yearling Chinook salmon (O. tshawytscha), sub-yearling Chinook salmon, and sockeye salmon (O. nerka) during out-migration from the lower Snake River to the Pacific Ocean during an 11-year study period (2008–2018). Results indicated that probabilities of avian consumption varied greatly across salmonid populations, bird species, colony location, river reach, and year. Cumulative consumption probabilities (consumption by birds from all colonies combined) were consistently the highest for steelhead, with annual estimates ranging from 0.22 (95% credible interval = 0.20–0.26) to 0.51 (0.43–0.60) of available smolts. The cumulative effects of avian consumption were significantly lower for yearling and sub-yearling Chinook salmon, with consumption probabilities ranging annually from 0.04 (0.02–0.07) to 0.10 (0.07–0.15) and from 0.06 (0.3–0.09) to 0.15 (0.10–0.23), respectively. Avian consumption probabilities for sockeye salmon smolts was generally higher than for Chinook salmon smolts, but lower than for steelhead smolts, ranging annually from 0.08 (0.03–0.22) to 0.25 (0.14–0.44). Although annual consumption probabilities for birds from certain colonies were more than 0.20 of available smolts, probabilities from other colonies were less than 0.01 of available smolts, indicating that not all colonies of birds posed a substantial risk to smolt mortality. Consumption probabilities were lowest for small colonies and for colonies located a considerable distance from the Snake and Columbia rivers. Total mortality attributed to avian consumption was relatively small for Chinook salmon (less than 10%) but was the single greatest source of mortality for steelhead (greater than 50%) in all years evaluated. Results suggest that the potential benefits to salmonid populations of managing birds to reduce smolt mortality would vary widely depending on the salmonid population, the species of bird, and the size and location of the breeding colony.

The evolution of the modern dam conflict on the Snake River, USA

ABSTRACT As dams age and values shift, communities face dam removal decisions that involve navigating complex social, economic and ecological interactions. Sometimes, this results in decades-long conflicts, such as that over the removal of the four lower Snake River dams (LSRD) in Washington State, USA – the focus of this study. We apply a broad analytical framework to understand how key factors in this conflict perpetuate it. We find that western science and economic expertise are politicized, and that while venues and geographies for stakeholder engagement are expanding, these shifts are not powerful enough to interrupt the cycle of litigation sustaining the LSRD debate.

A Computational Analysis of the Dynamics of R Style Based on 108 Million Lines of Code from All CRAN Packages in the Past 21 Years

The flexibility of R and the diversity of the R community leads to a large number of programming styles applied in R packages. We have analyzed 108 million lines of R code from CRAN and quantified the evolution in popularity of 12 style-elements from 1998 to 2019. We attribute 3 main factors that drive changes in programming style: the effect of style-guides, the effect of introducing new features, and the effect of editors. We observe in the data that a consensus in programming style is forming, such as using lower snake case for function names (e.g. softplus_func) and \<- rather than = for assignment.

Stochastic Dominance of Renewables to Replace Hydropower Under Policy Uncertainty

Regional energy managers and decision-makers face a world where climate change is introducing uncertainty over future power generation, as well as financial impacts from potential carbon taxation. A unique opportunity to explore is the rising interest in hydropower substitution with renewable resources, either to promote ecosystem services such as increasing the survivability of migratory fish or mitigating future loss of generation due to severe drought conditions. To address these concerns, a case study of the Columbia River Basin was conducted to evaluate the substitution of four Lower Snake River dams. A multistage methodology was chosen to evaluate grid adequacy, climate change performance, and the implications of tax uncertainty on the substitution portfolios. A specialized energy model was used to provide the adequacy and input for a Monte Carlo simulation to test the impact of an uncertain tax. The outcome is a carbon tax strategy region that suggests preferences under different taxes for risk-averse decision makers, alongside adequacy and climate metrics. We conclude that policymakers should consider a carbon tax between <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\$ $ </tex-math></inline-formula> 86 and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\$ $ </tex-math></inline-formula> 132 to incentivize a portfolio that marginally reduces emissions compared to the pre-dam removal baseline or a tax greater than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\$ $ </tex-math></inline-formula> 135 to incentivize another portfolio that significantly reduces emissions. This study makes three important contributions: (1) it provides a methodology for evaluating electricity generating portfolios in the presence of a carbon tax, (2) it evaluates adequacy metrics for technology substitutions with intermittent alternatives and climate change impacts, and (3) it offers specific guidance for energy policy making.

Salmon Versus Power: Dam Removal and Power Supply Adequacy

Dam removal is gaining both support and resistance in different communities and political circles in the Pacific Northwest of the United States, given its sensitive environmental and economic consequences. The Columbia River Basin (CRB) offers a unique opportunity to examine to what extent the replacement of hydroelectric dams affects reliability and adequacy of the power system given long-standing proposals to remove the four Lower Snake River dams to improve the survival of the endangered salmon species. Key results show that replacing the four dams leads to an inadequate energy supply, necessitating the need for more capacity to satisfy requirements. Although the four dams have higher nameplate capacity, they provide a much lower effective capacity. Thus, the debate about removing dams should be an opportunity for CRB managers to consider investment options in new ecosystem services and energy solutions that maintain adequate performance.

Snake River: A Navigation and Spawning Dilemma

The Snake River in northwestern United States is 1735 km long, the largest tributary of the Columbia River and is the 13th longest river in the United States. The Snake River drainage basin includes parts of six U.S. states. The Snake River Plain was created by a volcanic hotspot that lies beneath Yellow-stone National Park. The previous Ice Age carved out canyons, cliffs and waterfalls along the middle and lower Snake River. The Missoula Flood was to the north and Bonneville Flood to the south altered the Snake River and surrounding landscape. The Snake River has a drainage basin of 282,000 km2 in the states of Oregon, Washington, Utah, Nevada and Idaho. The Snake River drops from mountain elevations of 3000 m to its confluence with the Columbia River. The river is one of the most biologically diverse freshwater systems in the United States with trails designed to promote recreational tourism, increase use of the Snake River and create generations of people who care about the river and are willing to protect and provide environmental stewardship of the river watershed resources.

The Mistake on the Snake: The Lower Snake River Dams

Congressman Mike Simpson’s proposal to remove the four federal dams on the Lower Snake River (LSR) has reenergized the longstanding debate over the future of those dams, their narrow benefits, and their substantial costs, particularly to Endangered Species Act-listed Snake River salmon. This article examines the LSR dams, their history and justification, their role in sending Snake River on a path toward extinction from which they have yet to recover, and their impending liabilities under the Endangered Species and Clean Water Acts. The Simpson proposal, while arresting, is so freighted with spending on replacement power and river navigation improvements, for example, that its estimated $33.5 billion price tag seems wholly unrealistic. And its dam license extensions throughout the Columbia Basin and the litigation moratorium it would impose until the mid-21st century have generated such substantial opposition that enactment by Congress, in anything resembling its current form, will have to overcome the longest of odds. Still, given the imperiled nature of Snake River salmon and the considerable economic benefits that restored salmon runs could play in revitalizing the central Idaho economy, the proposal may serve as a beginning for Idaho’s elected officials and its public to focus on the advantages that restored Idaho salmon runs could play in revitalizing the central Idaho economy. Anything resembling the Simpson proposal should be welcomed as a considerable economic stimulus for the region.

Contemporary genetic structure affects genetic stock identification of steelhead trout in the Snake River basin.

Genetic stock identification is a widely applied tool for the mixed‐stock management of salmonid species throughout the North Pacific Rim. The effectiveness of genetic stock identification is dependent on the level of differentiation among stocks which is often high due to the life history of these species that involves high homing fidelity to their natal streams. However, the utility of this tool can be reduced when natural genetic structuring has been altered by hatchery translocation and/or supplementation. We examined the genetic population structure of ESA‐listed steelhead in the Snake River basin of the United States. We analyzed 9,613 natural‐origin adult steelhead returning to Passive Integrated Transponder detection sites throughout the basin from 2010 through 2017. Individuals were genotyped at 180 single nucleotide polymorphic genetic markers and grouped into 20 populations based on their return location. While we expected to observe a common pattern of hierarchical genetic structuring due to isolation by distance, we observed low genetic differentiation between populations in the upper Salmon River basin compared to geographically distant populations in the lower Snake River basin. These results were consistent with lower genetic stock assignment probabilities observed for populations in this upper basin. We attribute these patterns of reduced genetic structure to the translocation of lower basin steelhead stocks and ongoing hatchery programs in the upper Salmon River basin. We discuss the implications of these findings on the utility of genetic stock identification in the basin and discuss opportunities for increasing assignment probabilities in the face of low genetic structure.

Exploration of Environmental DNA (eDNA) to Detect Kirtland's Snake (Clonophis kirtlandii).

Simple SummarySmall and difficult to find species of conservation concern such as the Kirtland’s Snake require significant survey effort using traditional methods. Surveying for DNA shed into the environment, or environmental DNA, we set out to improve detection probability and efficiency to aid in future conservation efforts for this species. Field surveys revealed temporal and spatial variation in Kirtland’s Snake activity. More snakes were found in the spring, during the first field season, and in areas with abundant grass, herbaceous vegetation, and shrubs. We collected environmental samples and developed a molecular assay to detect eDNA across this spatial and temporal gradient of snake activity. We also tested the persistence of DNA in the microenvironment snakes are expected to use by introducing feces into artificial burrows. We were able to detect snake eDNA in only a single environmental sample and found that eDNA in artificial burrows appears to decline within a week. We explored the potential methodological and biological causes of this low detection success to aid future research employing eDNA detection as a survey method in snakes.Environmental DNA (eDNA) surveys utilize DNA shed by organisms into their environment in order to detect their presence. This technique has proven effective in many systems for detecting rare or cryptic species that require high survey effort. One potential candidate for eDNA surveying is Kirtland’s Snake (Clonophis kirtlandii), a small natricine endemic to the midwestern USA and threatened throughout its range. Due to its cryptic and fossorial lifestyle, it is also a notoriously difficult snake to survey, which has limited efforts to understand its ecology. Our goal was to utilize eDNA surveys for this species to increase detection probability and improve survey efficiency to assist future conservation efforts. We conducted coverboard surveys and habitat analyses to determine the spatial and temporal activity of snakes, and used this information to collect environmental samples in areas of high and low snake activity. In addition, we spiked artificial crayfish burrows with Kirtland’s Snake feces to assess the persistence of eDNA under semi-natural conditions. A quantitative PCR (qPCR) assay using a hydrolysis probe was developed to screen the environmental samples for Kirtland’s Snake eDNA that excluded closely related and co-occurring species. Our field surveys showed that snakes were found in the spring during the first of two seasons, and in areas with abundant grass, herbaceous vegetation, and shrubs. We found that eDNA declines within a week under field conditions in artificial crayfish burrows. In environmental samples of crayfish burrow water and sediment, soil, and open water, a single detection was found out of 380 samples. While there may be physicochemical and biological explanations for the low detection observed, characteristics of assay performance and sampling methodology may have also increased the potential for false negatives. We explored these outcomes in an effort to refine and advance the successful application of eDNA surveying in snakes and groundwater microhabitats.

Dammed If You Don’t, But What If You Do? Breaching the Lower Snake River Dams in Washington State

Four dams on the lower Snake River in Washington State generate hydropower and allow for regional agriculture and barge shipping to Portland OR. However, the dams impede the migration of local salmon populations (Oncorhynchus spp.), which are in steep decline, and drastically impact the populations of salmon and orca whales, for whom salmon are a primary food source. For years, environmental groups have argued for breaching the dams; other interests counter that the dams are too critical to the economy of the region to lose; and federal agencies assert that the dams can remain and salmon populations will recover with mitigation techniques. Scientific and economic analyses, litigation, and elected officials’ efforts have not been able to move the issue towards a solution. Readers will examine the interests of primary actors in the issue, how they influence the policy process, the role of scientific and economic analyses, and possible approaches for resolving the issue.

Trichome morphology relates to taxonomic diversity in Monardella (Lamiaceae) in the lower Snake River Watershed of Idaho and Oregon, USA: Taxonomic studies in Monardella (Lamiaceae) VI

Monardella is a western North America genus ranging from the Rocky Mountains to the Pacific Ocean and from southern Canada to the southern tip of Baja California Sur. The levels of unrecognized and cryptic taxa within Monardella are similar to other taxonomically complicated western North American genera, such as Eriogonum (Polygonaceae), Penstemon (Plantaginaceae), and Oreocarya (Boraginaceae). We present variation in trichome morphology as a taxonomic tool within Monardella, being comparable in importance to trichome variation in other plant families and genera (e.g., Brassicaceae, Draba; Loasaceae, Mentzelia; Solanaceae, Solanum). Trichome morphology within Monardella is a useful character to differentiate taxa and resolve taxonomic ambiguities. We present nomenclatural novelties and revisions for Monardella occurring in the Hells Canyon region along the lower Snake River of west-central Idaho and northeastern Oregon. We introduce the following taxonomic and nomenclatural changes. Monardella odoratissima Benth. var. neglecta Cronquist is recognized as a later homonym; a new name and rank are presented for it: M. perplexans Elvin, R. B. Kelley, & B. T. Drew. Two new species are described: M. kruckebergii Elvin, R. B. Kelley, & B. T. Drew and M. walwaamaxsia Elvin, R. B. Kelley, & B. T. Drew.

Difficulties for cost-benefit analysis in the 2020 environmental impact statement to recover the endangered wild salmon and steelhead in the Columbia River Basin.

Runs of the endangered wild salmon/steelhead in the Columbia River basin may be only two to seven percent of historic levels. These fish are a common-pool resource, where stakeholders over-consume, pollute rivers and oceans, block passage with dams and culverts, operate net pen fish farms, and plant huge numbers of hatchery fish that compete with and hybridize wild fish. Rivers provide free or subsidized services that stakeholders covet, however recovery of the endangered wild fish requires that peoples utilizing the rivers and the ocean must constrain their behavior, often reducing their profit. A new Environmental Impact Statement (EIS) and cost-benefit analysis are in progress for recovery of the endangered wild salmon/steelhead in the Columbia River basin. New regulations require surveys of U.S. households to measure the non-use benefits of salmon/steelhead recovery that can be important for endangered species. We review the 2002 EIS for juvenile salmon migration on the lower Snake River tributary to find mistakes to avoid in the new EIS and in other recovery studies.

Removal pattern mitigates negative, short‐term effects of stepwise Russian olive eradication on breeding birds

AbstractInvasive species can have disastrous ecological consequences, and management is often required to control these invasions and mitigate the damage. Yet in many systems, biological invaders can serve critical ecological roles, particularly where they have been long‐established or effectively replaced functionally similar native species. In such cases, eradicating invasions can have unintended consequences on other components of the ecosystem, and potential control measures must be viewed within an ecosystem‐wide context to ensure they do not cause more harm than good. On the lower Snake River in eastern Washington, invasive Russian olive (Elaeagnus angustifolia) comprises 90% of the woody riparian vegetation in some areas. In this study, we experimentally removed half of the Russian olive from 0.5‐ha plots using three configuration patterns that varied in the amount of interspersion of remaining vegetation (n = 9 replicates) to evaluate the short‐term impact of a stepwise restoration strategy on breeding bird communities. We monitored plots for 5 yr and found that Russian olive removal on low interspersion treatments negatively affected occupancy rates for 50 of 52 species (96%) and significantly reduced richness by up to 2.41 (95% credible interval [CI] = 0.73, 4.14) species relative to control plots. These effects dampened with increasing interspersion, and occupancy rates of only 41 (79%) species decreased on high interspersion treatments, leading to non‐significant richness reductions of only 0.99 (95% CI = −0.70, 2.75) species. Given the dominance of Russian olive in this region, removing it eliminates critical habitat for birds that require woody structure for nesting and foraging. Thus, we caution managers to consider the potential short‐term negative impacts to the local fauna when planning invasive control efforts. However, we found that several riparian‐dependent species known to breed in the region were noticeably absent from our study plots, and short‐term losses in avian habitat may be tolerable where restoration of native vegetation supports greater diversity in the long term. In such restoration efforts, managers may be able to mitigate the negative effects of invasive shrub control by maintaining high interspersion among unmanipulated vegetation while waiting for native vegetation to re‐establish.

Thermal exposure of adult Chinook salmon and steelhead: Diverse behavioral strategies in a large and warming river system

Rising river temperatures in western North America have increased the energetic costs of migration and the risk of premature mortality in many Pacific salmon (Oncorhynchus spp.) populations. Predicting and managing risks for these populations requires data on acute and cumulative thermal exposure, the spatio-temporal distribution of adverse conditions, and the potentially mitigating effects of cool-water refuges. In this study, we paired radiotelemetry with archival temperature loggers to construct continuous, spatially-explicit thermal histories for 212 adult Chinook salmon (O. tshawytscha) and 200 adult steelhead (O. mykiss). The fish amassed ~500,000 temperature records (30-min intervals) while migrating through 470 kilometers of the Columbia and Snake rivers en route to spawning sites in Idaho, Oregon, and Washington. Spring- and most summer-run Chinook salmon migrated before river temperatures reached annual highs; their body temperatures closely matched ambient temperatures and most had thermal maxima in the lower Snake River. In contrast, many individual fall-run Chinook salmon and most steelhead had maxima near thermal tolerance limits (20–22 °C) in the lower Columbia River. High temperatures elicited extensive use of thermal refuges near tributary confluences, where body temperatures were ~2–10 °C cooler than the adjacent migration corridor. Many steelhead used refuges for weeks or more whereas salmon use was typically hours to days, reflecting differences in spawn timing. Almost no refuge use was detected in a ~260-km reach where a thermal migration barrier may more frequently develop in future warmer years. Within population, cumulative thermal exposure was strongly positively correlated (0.88 ≤ r ≤ 0.98) with migration duration and inconsistently associated (-0.28 ≤ r ≤ 0.09) with migration date. All four populations have likely experienced historically high mean and maximum temperatures in recent years. Expected responses include population-specific shifts in migration phenology, increased reliance on patchily-distributed thermal refuges, and natural selection favoring temperature-tolerant phenotypes.

The Fight Over Columbia Basin Salmon Spills and the Future of the Lower Snake River Dams

One of the nation’s most longstanding environmental-energy conflicts concerns the plight of numerous Columbia Basin salmon species which must navigate the Federal Columbia River Power System (FCRPS), a series of hydroelectric dams that make the basin one of the most highly developed in the world. Although the FCRPS dams produce a considerable amount of low-cost hydropower, the mortalities they cause due to the construction and operation of FCRPS dams led to Endangered Species Act listings for the basin’s salmon. Since those listings a quarter-century ago, the federal government has struggled to produce biological opinions that can survive judicial scrutiny, repeatedly failing to do so. The latest round of litigation resulted in renewed directive from the federal district court of Oregon to revise the current biological opinion and to spill water at several dams in the interim to facilitate salmon migration. The directive to spill was upheld by the Ninth Circuit in 2018, but the U.S. House of Representatives quickly voted to overturn that decision, and the Senate now has the matter under consideration. This article considers the latest round of Columbia Basin salmon litigation and the threat of congressional intervention. We also examine the fate of four Snake River FCRPS dams that have proved particularly hazardous to listed salmon. These dams provide no flood control, easily replaceable power, and barge navigation for which there are also ready substitutes. The article maintains that since these four dams can pass no reasonable cost-benefit test, Congress should not act to revise the court-ordered spills but instead order the lower Snake River dams removed, which would begin the restoration the listed Snake River salmon and result in the transformation of the economy of the Snake Basin in eastern Washington and Oregon, and in Idaho.