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Many fishways were designed to facilitate upstream migration at anthropogenic barriers for targeted species, such as salmonids, though these designs may impede the passage of non-target species with different swimming capabilities. Developing passage metrics that quantify hydraulic conditions scaled to biological behaviours or traits could identify the causes of challenging passage conditions and aid design of multi-species fishways. Our objective was to test the performance of six velocity- and turbulence-derived metrics for predicting passage behaviours of Pacific Lamprey (Entosphenus tridentatus) under varying hydraulic conditions within an experimental vertical slot. These metrics were the 1) swim path-averaged water velocity, 2) swim path-averaged turbulence kinetic energy ( TKE ¯ ), 3) power, 4) work, 5) a biological turbulence intensity, I ¯ Bio , quantified as the ratio between the root of the TKE ¯ and a biological criterion (the bulk average velocity for which lampreys shift from free-swimming to attachment behaviours, UBio = 1.8 m·s−1) and 6) a flow index I ¯ Bio , which is I ¯ Bio modulated by a dimensionless velocity U* = U/UBio, where U is the mean flow through the vertical slot. We assessed the performance of these metrics by evaluating their relationship with Pacific Lamprey attachment time, which serves as an important behavioural proxy for passage difficulty. Only I ¯ Bio and F were significantly associated with attachment time and we suggest these metrics can be adapted for other fish species based on velocity thresholds inducing key behavioural responses. More broadly, our study demonstrates the importance of accounting for turbulence and employing biological criteria when quantifying fish passage within or across species. [ABSTRACT FROM AUTHOR]

The melting cryosphere adds heterogeneity to the abiotic and biotic characteristics of many high latitude and montane rivers. However, climate change threatens the cryosphere's persistence in many regions. While existing research has explored the impacts of cryospheric loss on the diversity and structure of freshwater communities, implications for functional traits of communities, such as production of aquatic invertebrates, remain unresolved. Here, we quantified aquatic invertebrate community structure and secondary production in southeast Alaska (USA) streams that represent a meltwater to non‐meltwater gradient, including streams fed primarily by: (1) glacier‐melt, (2) snowmelt, (3) rainfall, and (4) a combination of these sources. We found alpha diversity was highest in the snow‐fed stream and lowest in the glacier‐fed stream. Annual secondary production was also lowest in the glacier‐fed stream (0.56 g ash‐free dry mass m−2), but 2–5 times higher in the other stream types primarily due to greater production of shared taxa that were found in all streams. However, despite low invertebrate diversity and productivity, the glacier‐fed stream hosted distinct species assemblages associated with unique cycles of stream flow, water temperature, turbidity, and nutrient concentrations, which contributed to higher beta diversity between streams. Our findings suggest that the loss of glacier‐melt contributions to rivers may result in increased freshwater invertebrate production but reduced beta diversity, which could have implications for community stability and the capacity of landscapes to support higher‐level consumers, including fishes. [ABSTRACT FROM AUTHOR]

We used biotelemetry and genetic stock identification to assess sea-to-sea survival and run composition of 1212 late-migrating adult steelhead (anadromous Oncorhynchus mykiss) through the Columbia River and Snake River migratory corridors. The late run was predominated by steelhead from Idaho's Clearwater and Salmon rivers that must pass eight large hydroelectric dams during both prespawn and postspawn migrations. In 2 years (2013 and 2014), prespawn survival to Snake River tributaries (>500 km) was 0.48-0.67 for the most abundant populations and was higher for females and 1-sea fish (i.e., fish that spend one winter at sea). Annual survival from Snake River tributary entry to postspawn kelt status was 0.14-0.17, with higher survival for females and those without hatchery fin clips. Kelt outmigration survival was 0.31-0.39 past four Snake River dams and 0.13-0.20 past all eight dams and was highest for smaller kelts. Full-cycle adult freshwater survival (sea-to- sea) including 16 dam passage events was 0.01-0.02. Younger steelhead and those without fin clips survived at the highest rates. This study uniquely partitioned mortality across prespawn, reproductive, and kelt life history stages and informs management strategies for this conservation-priority metapopulation. Nous avons utilise la biotelemetrie et l'identification genetique du stock pour evaluer la survie de l'ocean a l'ocean et la composition de la montaison de 1212 truites arc-en-ciel anadromes (Oncorhynchus mykiss) a migration tardive dans les corridors de migration du fleuve Columbia et de la riviere Snake. Des truites arc-en-ciel anadromes provenant des rivieres Clearwater et Salmon en Idaho etaient predominantes dans la migration tardive, ces truites devant franchir huit grands barrages hydroelectriques durant leurs migrations avant et apres le frai. En 2 ans (2013 et 2014), le taux de survie avant le frai jusqu'a des affluents de la Snake (>500 km) etait de 0,48-0,67 pour les populations les plus abondantes et etait plus eleve pour les femelles et les individus ayant ete dans l'ocean une fois. La survie annuelle de l'entree dans les affluents de la riviere Snake jusqu'a l'etat de charognard etait de 0,14-0,17, les taux les plus eleves etant observes pour les femelles et les individus sans marque d'ablation de nageoire en aleviniere. Les taux de survie des charognards durant la devalaison etaient de 0,31-0,39 apres quatre barrages sur la riviere Snake et de 0,13-0,20 apres tous les huit barrages, et ce taux etait le plus eleve pour les charognards plus petits. Le taux de survie en eau douce des adultes apres un cycle complet (ocean a ocean) comptant 16 franchissements de barrage etait de 0,01-0,02. Les truites arc-en-ciel anadromes plus jeunes et celles sans marque d'ablation de nageoire en aleviniere presentaient les taux de survie les plus eleves. L'etude distingue nettement la mortalite des stades pregenesique, reproducteur et de charognard du cycle biologique et fournit de l'information utile pour l'elaboration de strategies de gestion pour cette metapopulation dont la conservation est prioritaire. [Traduit par la Redaction], Introduction Preservation of genetic and life history diversity are becoming increasingly important objectives in fish conservation and management programs. In the United States, the Endangered Species Act has essentially codified [...]

Adaptive capacity can present challenges for modelling as it encompasses multiple ecological and evolutionary processes such as natural selection, genetic drift, gene flow and phenotypic plasticity. Spatially explicit, individual‐based models provide an outlet for simulating these complex interacting eco‐evolutionary processes. We expanded the existing Cost‐Distance Meta‐POPulation (CDMetaPOP) framework with inducible plasticity modelled as a habitat selection behaviour, using temperature or habitat quality variables, with a genetically based selection threshold conditioned on past individual experience. To demonstrate expected results in the new module, we simulated hypothetical populations and then evaluated model performance in populations of redband trout (Oncorhynchus mykiss gairdneri) across three watersheds where temperatures induce physiological stress in parts of the stream network. We ran simulations using projected warming stream temperature data under four scenarios for alleles that: (1) confer thermal tolerance, (2) bestow plastic habitat selection, (3) give both thermal tolerance and habitat selection preference and (4) do not provide either thermal tolerance or habitat selection. Inclusion of an adaptive allele decreased declines in population sizes, but this impact was greatly reduced in the relatively cool stream networks. As anticipated with the new module, high‐temperature patches remained unoccupied by individuals with the allele operating plastically after exposure to warm temperatures. Using complete habitat avoidance above the stressful temperature threshold, habitat selection reduced the overall population size due to the opportunity cost of avoiding areas with increased, but not guaranteed, mortality. Inclusion of plasticity within CDMetaPOP will provide the potential for genetic or plastic traits and 'rescue' to affect eco‐evolutionary dynamics for research questions and conservation applications. [ABSTRACT FROM AUTHOR]

Impassable dams on major tributaries to the Willamette River, Oregon, have restricted access to historical spawning habitat for returning adult Chinook Salmon Oncorhynchus tshawytscha. To restore these populations, some fish are collected and transported in trucks upstream of dams (i.e., adult trap‐and‐haul operations). However, persistently high prespawn mortality (PSM) rates in these programs have hindered conservation efforts. The objective of this study was to evaluate environmental factors and individual fish traits associated with PSM in Chinook Salmon populations that were transported and released upstream of dams in three Willamette River tributaries. Annual PSM of tagged and untagged female salmon ranged from 6% to 88% across 7 years. Mortality was higher in warmer years and in warmer tributaries, consistent with rangewide studies of PSM in Chinook Salmon. Effects of individual traits were mixed across sites: longer salmon and those released relatively early or late in the migrations had higher mortality. We conclude that strategies designed to minimize adult Chinook Salmon exposure to warm water temperatures, as well as additional research into both proximate and ultimate causes of PSM, may lead to better management and conservation outcomes for outplanted populations, including those in Willamette River tributaries. [ABSTRACT FROM AUTHOR]

Aquatic ectotherms are predicted to harbour genomic signals of local adaptation resulting from selective pressures driven by the strong influence of climate conditions on body temperature. We investigated local adaptation in redband trout (Oncorhynchus mykiss gairdneri) using genome scans for 547 samples from 11 populations across a wide range of habitats and thermal gradients in the interior Columbia River. We estimated allele frequencies for millions of single nucleotide polymorphism loci (SNPs) across populations using low‐coverage whole genome resequencing, and used population structure outlier analyses to identify genomic regions under divergent selection between populations. Twelve genomic regions showed signatures of local adaptation, including two regions associated with genes known to influence migration and developmental timing in salmonids (GREB1L, ROCK1, SIX6). Genotype–environment association analyses indicated that diurnal temperature variation was a strong driver of local adaptation, with signatures of selection driven primarily by divergence of two populations in the northern extreme of the subspecies range. We also found evidence for adaptive differences between high‐elevation desert vs. montane habitats at a smaller geographical scale. Finally, we estimated vulnerability of redband trout to future climate change using ecological niche modelling and genetic offset analyses under two climate change scenarios. These analyses predicted substantial habitat loss and strong genetic shifts necessary for adaptation to future habitats, with the greatest vulnerability predicted for high‐elevation desert populations. Our results provide new insight into the complexity of local adaptation in salmonids, and important predictions regarding future responses of redband trout to climate change. [ABSTRACT FROM AUTHOR]

Fishways designed for salmonids often restrict passage by non-salmonids, and effective tools are needed both to identify passage problems for nontarget species and to inform remediation planning. In this case study, we used migration histories from 2170 radio-tagged adult Pacific lamprey (Entosphenus tridentatus) to identify locations of poor passage (bottlenecks) at a large, multifishway dam. Over 10 years, 49% of tagged lamprey that entered fishways failed to pass the dam. Models accounting for repeated attempts by individual lamprey indicated successful passage strongly depended on attempted passage route. Success also varied with time of fishway entry, water temperature, and lamprey body size. Most failed passage attempts terminated in lower fishway segments, but extensive seasonal shifts in bottleneck locations were detected. Ranking metrics helped prioritize bottlenecks and identified sites where structural or operational modifications should improve lamprey passage. Our integration of spatially intensive monitoring with novel analytical techniques was critical to understanding the complex relationships among fishway features, environmental variation, and lamprey behavior. The prioritization framework can be applied to a wide range of fish passage assessments. Les passes migratoires concues pour les salmonides restreignent souvent le passage d'autres poissons, et des outils efficaces sont necessaires pour cerner les problemes associes au passage d'especes non visees et eclairer la planification de mesures correctives. Dans la presente etude de cas, nous avons utilise les historiques de migration de 2170 lamproies du Pacifique (Entosphenus tridentatus) adultes munies de radio-emetteurs pour cerner les lieux de passage difficiles (goulots d'etranglement) a un important barrage comptant plusieurs passes. Sur une periode de 10 ans, 49% des lamproies munies d'emetteurs qui entraient dans ces passes ne reussissaient pas a remonter le barrage. Des modeles tenant compte de tentatives multiples par les memes lamproies ont indique que le succes du passage dependait fortement de la voie de passage employee. Le taux de succes variait egalement selon le moment de l'entree dans la passe, la temperature de l'eau et la taille du corps de la lamproie. La plupart des tentatives de passage infructueuses prenaient fin dans des sections avals des passes, mais d'importantes variations saisonnieres de l'emplacement des goulots d'etranglement ont ete decelees. Le classement des differents parametres a aide a etablir la priorite des goulets et a cerner les sites ou des modifications structurales ou operationnelles devraient ameliorer le passage des lamproies. L'integration d'une surveillance spatiale fine et de nouvelles techniques analytiques s'est averee essentielle a une meilleure comprehension des liens complexes entre les caracteristiques des passes a poissons, les variations des conditions du milieu et le comportement des lamproies. Le cadre d'etablissement de la priorite peut etre applique a un vaste eventail devaluations de passes a poissons. [Traduit par la Redaction], Introduction River systems worldwide have been fragmented by dams and other anthropogenic obstacles that restrict fish movements (Nilsson et al. 2005). A diverse array of fishways and other passage systems [...]

Increasing pinniped abundance in the Pacific Northwest has coincided with population declines of Pacific salmon (Oncorhynchus spp.) and steelhead trout (Oncorhynchus mykiss), and concentrated predation may affect the recovery of some threatened and endangered salmonid stocks. We used radiotelemetry to evaluate pinniped-caused injury effects on migration survival of 17 007 adult Columbia River Chinook salmon (Oncorhynchus tshawytscha) and steelhead trout. Injuries from pinnipeds were common (mean injury rate across 29 run-years = 36.5%) and were most common for spring Chinook salmon and steelhead trout. Injury was not consistently associated with adult survival to spawning tributaries, but some negative survival effects were detected. Pinniped-caused injury rates decreased as annual run sizes increased, indicating density-dependent or saturation effects. Within a run, large fish generally had a higher injury incidence than small fish, suggesting pinnipeds targeted large fish or more efficiently captured small fish. Seasonal, size- dependent, and density-dependent results imply that pinniped effects likely differ widely among salmonid populations within the Columbia River basin. A better understanding of these effects is needed to guide management and conservation strategies. L'augmentation d'abondance des pinnipedes dans le Nord-Ouest Pacifique coincide avec les declins demographiques des saumons du Pacifique (Oncorhynchus spp.) et de la truite arc-en-ciel anadrome (Oncorhynchus mykiss)etla concentration de la predation peut affecter le retablissement de quelques stocks de salmonides menaces et en peril. La radiotelemetrie nous a servi a evaluer les effets des blessures causees par les pinnipedes sur la survie durant la migration de 17 007 saumons chinook (Oncorhynchus tshawytscha) et truites arc-en-ciel anadromes adultes dans le fleuve Columbia. Les blessures dues aux pinnipedes sont communes (taux moyen de blessures dans 29 montaisons-annees = 36,5%) et sont plus abondantes chez les saumons chinook et truites arc-en-ciel anadromes de printemps. Il n'y a pas d'association constante entre les blessures et la survie des adultes jusqu'aux tributaires de fraie, mais on peut deceler des effets negatifs sur la survie. Les taux de blessures dues aux pinnipedes diminuent a mesure que la taille des montaisons annuelles augmente, ce qui indique des effets de densite dependance ou de saturation. Dans une montaison, les poissons plus grands ont generalement une incidence plus elevee de blessures que les poissons plus petits, ce qui laisse croire que les pinnipedes ciblent les poissons plus grands ou alors capturent plus efficacement les plus petits. Ces resultats saisonniers et dependants de la taille et de la densite amenent a croire que les effets des pinnipedes different vraisemblablement beaucoup d'une population de salmonides a une autre au sein du bassin versant du Columbia. Une meilleure comprehension de ces effets est requise pour orienter les strategies de gestion et de conservation. [Traduit par la Redaction], Introduction Members of the Order Pinnipedia evolved >20 million years ago, and their distributions have likely overlapped those of Pacific anadromous salmonids (Oncorhynchus spp.) for much of their existence. Many [...]

Abstract: The relationships among behavior, environment, and migration success in anadromous fishes are poorly understood. We monitored migration behavior at eight Columbia and Snake river dams for 18 286 adult [...]

Abstract: Upstream-migrating adult salmon must make a series of correct navigation and route-selection decisions to successfully locate natal streams. In this field study, we examined factors influencing migration route selections [...]

Similar to many fish, juvenile Pacific salmon rearing in temperate streams face a growth and survival bottleneck early in their first summer due to limitations in space and food. Fish carcasses have been shown to affect juvenile salmon growth in many systems, but carcasses likely also alter behavioral and dispersal response of hatchery‐origin young‐of‐the‐year salmon. We tested the social and emigration response of subyearling chinook salmon to carcasses of Pacific lamprey or rainbow trout using semi‐open flow‐through mesocosm experiments. We expected the presence of carcasses to increase salmon growth and density while decreasing intraspecific aggression and downstream emigration compared to controls without carcasses. Consistent with expectations, salmon emigrated at lower rates when carcasses were present, resulting in significantly higher holding densities. Contrary to our expectations and results from previous studies, we did not detect differences in growth rate of juvenile salmon among treatments. Our findings suggest that indirect responses of consumers to concentrated resources may have measurable effects on density mediated by movement behaviors. Differences in lamprey and trout decomposition also suggest that carcass traits mediate the behavioral responses of consumers and incorporation of carcass subsidies into food webs. [ABSTRACT FROM AUTHOR]

Fishways have been widely used for upstream passage around human-built structures, but 'success' has varied dramatically. Evaluation of fishway success has typically been conducted at local scales using metrics such as fish passage efficiency and passage time, but evaluations are increasingly used in broader assessments of whether passage facilities meet population-specific conservation and management objectives. Over 15 years, we monitored passage effectiveness at eight dams on the Columbia and Snake rivers for 26,886 radio-tagged spring-summer and fall Chinook Salmon O. tshwaytscha, Sockeye Salmon O. nerka, and summer steelhead O. mykiss during their migrations to spawning sites. Almost all fish that entered dam tailraces eventually approached and entered fishways. Tailrace-to-forebay passage efficiency estimates at individual dams were consistently high, averaging 0.966 (SD = 0.035) across 245 run×year×dam combinations. These estimates are among the highest recorded for any migratory species, which we attribute to the scale of evaluation, salmonid life history traits (e.g., philopatry), and a sustained adaptive management approach to fishway design, maintenance, and improvement. Full-dam fish passage times were considerably more variable, with run×year×dam medians ranging from 5–65 h. Evaluation at larger scales provided evidence that fishways were biologically effective, e.g., we observed rapid migration rates (medians = 28–40 km/d) through river reaches with multiple dams and estimated fisheries-adjusted upstream migration survival of 67–69%. However, there were substantive uncertainties regarding effectiveness. Uncertainty about natal origins confounded estimation of population-specific survival and interpretation of apparent dam passage 'failure', while lack of post-migration reproductive data precluded analyses of delayed or cumulative effects of passing the impounded system on fish fitness. Although the technical fishways are effective for salmonids in the Columbia-Snake River system, other co-migrating species have lower passage rates, highlighting the need for species-specific design and evaluation wherever passage facilities impact fish management and conservation goals. [ABSTRACT FROM AUTHOR]

Adaptive capacity is a topic at the forefront of environmental change research with roots in both social, ecological, and evolutionary science. It is closely related to the evolutionary biology concept of adaptive potential. In this systematic literature review, we: (1) summarize the history of these topics and related fields; (2) assess relationship(s) between the concepts among disciplines and the use of the terms in climate change research, and evaluate methodologies, metrics, taxa biases, and the geographic scale of studies; and (3) provide a synthetic conceptual framework to clarify concepts. Bibliometric analyses revealed the terms have been used most frequently in conservation and evolutionary biology journals, respectively. There has been a greater growth in studies of adaptive potential than adaptive capacity since 2001, but a greater geographical extent of adaptive capacity studies. Few studies include both, and use is often superficial. Our synthesis considers adaptive potential as one process contributing to adaptive capacity of complex systems, notes "sociological" adaptive capacity definitions include actions aimed at desired outcome (i.e., policies) as a system driver whereas "biological" definitions exclude such drivers, and suggests models of adaptive capacity require integration of evolutionary and social–ecological system components. [ABSTRACT FROM AUTHOR]

Adult summer‐run steelhead Oncorhynchus mykiss overwinter in freshwater for several months prior to spawning. In systems supporting mixed populations of fisheries and conservation importance, understanding the distribution and survival of pre‐ and postspawn fish is necessary for informed management. The upper Columbia River supports hatchery‐origin components valued by anglers, natural‐origin components of conservation concern, and temporary strays from downstream populations. We used radiotelemetry and PIT telemetry to monitor the behavior, distribution, and survival of adult steelhead during fall, overwintering, spawning, and postspawn periods, with a focus on use of the main stem versus four major tributaries. Adult steelhead (N = 807) were tagged at Priest Rapids Dam in 2015 and 2016. One‐fifth of steelhead fell back below Priest Rapids Dam and did not reascend. A slight majority of tagged steelhead that overwintered upstream of Priest Rapids Dam did so in main‐stem reservoirs (54%; N = 548). Overwintering in the main‐stem Columbia River was more likely for later‐arriving steelhead and was concentrated in the upstream‐most reservoir. Winter tributary use was highest in the Wenatchee (26%; 2016) and Methow (18%; 2015) rivers, whereas no steelhead overwintered in the Entiat River. Harvest of hatchery‐origin steelhead was 18% in 2015 and was near zero in 2016, when the fishery was suspended due to low adult returns. After accounting for reported harvest, annual overwinter survival did not differ between main‐stem and tributary habitats, and relatively low adjusted survival of hatchery‐origin steelhead in 2015 suggested unreported harvest. In contrast to low iteroparity rates (<3%), the majority of postspawn steelhead (56.5%) exited tributaries as kelts; kelt survival to Bonneville Dam was 65% in 2016 and 23% in 2017. Collectively, the results highlight the importance of understanding patterns of habitat use and mortality in steelhead populations when managers are faced with balancing harvest and conservation goals. [ABSTRACT FROM AUTHOR]

Typically, fish passage design is informed by a critical velocity model whereby fish are assumed to fail passage if the water velocity is higher than the critical swim speed, an assumption that may not be met when locomoting fish are partially submerged. We applied a drag force model (DFM) approach for use in design of Pacific Lamprey (Entosphenus tridentatus) Passage Structures (LPS) where lamprey may be partially or fully submerged. Our investigation assessed the dead-drag forces at four levels of static submergence: fully submerged (120 mm), equally submerged (40 mm), partially submerged (15 mm), and skin-flow (5 mm) for a Pacific Lamprey physical model by varying simulated LPS slope and discharge conditions. We then used the results to establish drag force thresholds corresponding to the known critical velocity thresholds of Pacific Lamprey to predict passage success under partial and full submergence conditions. Consideration of drag force in fish passage could be used to improve or create species-specific design recommendations for fishways, or to inform the design of barriers to prevent invasive species passage. The results suggest consideration of drag force in addition to velocity is beneficial to predict Pacific Lamprey passage success under partial submergence conditions. [ABSTRACT FROM AUTHOR]

High rates of dispersal can breakdown coadapted gene complexes. However, concentrated genomic architecture (i.e., genomic islands of divergence) can suppress recombination to allow evolution of local adaptations despite high gene flow. Pacific lamprey (Entosphenus tridentatus) is a highly dispersive anadromous fish. Observed trait diversity and evidence for genetic basis of traits suggests it may be locally adapted. We addressed whether concentrated genomic architecture could influence local adaptation for Pacific lamprey. Using two new whole genome assemblies and genotypes from 7,716 single nucleotide polymorphism (SNP) loci in 518 individuals from across the species range, we identified four genomic islands of divergence (on chromosomes 01, 02, 04, and 22). We determined robust phenotype‐by‐genotype relationships by testing multiple traits across geographic sites. These trait associations probably explain genomic divergence across the species' range. We genotyped a subset of 302 broadly distributed SNPs in 2,145 individuals for association testing for adult body size, sexual maturity, migration distance and timing, adult swimming ability, and larval growth. Body size traits were strongly associated with SNPs on chromosomes 02 and 04. Moderate associations also implicated SNPs on chromosome 01 as being associated with variation in female maturity. Finally, we used candidate SNPs to extrapolate a heterogeneous spatiotemporal distribution of these predicted phenotypes based on independent data sets of larval and adult collections. These maturity and body size results guide future elucidation of factors driving regional optimization of these traits for fitness. Pacific lamprey is culturally important and imperiled. This research addresses biological uncertainties that challenge restoration efforts. [ABSTRACT FROM AUTHOR]

Anadromous fish transport marine‐derived nutrients to freshwaters during spawning migrations with potential implications for stream food webs. While many studies have explored the role of marine‐derived nutrients instream ecosystems (particularly via Pacific salmonids [Oncorhynchus spp.]), relatively few have examined the spatial distribution and patchiness of non‐salmonid fish carcasses or rates of transport to the riparian zone.We radio‐tagged and released 144 mature Pacific lamprey (Entosphenus tridentatus) prior to spawning and tracked the fate of post‐spawn carcasses in two inland Columbia River basin streams to characterise spatial distribution of carcasses and marine‐derived nutrient deposition. We found that 27 and 40% of lamprey that could be assigned a fate were moved into the riparian zone adjacent to stream segments exhibiting higher velocity conditions with larger substrates. Conversely, lamprey with instream fates were associated with depositional microhabitats and woody debris dams. Estimated carcass loading rates varied by more than an order of magnitude among habitats. These patterns probably reflect a combination of processes influencing the likelihood of carcass removal (e.g. by predators or scavengers, or stranding) and factors affecting the distribution of carcasses remaining within the stream.Our results demonstrate substantial transport of lamprey carcasses across the stream‐riparian ecotone and a non‐random distribution of carcasses within streams, patterns which probably influence how resources enter stream and riparian food webs. More broadly, the results suggest local and landscape‐scale hydrogeomorphic factors, along with species‐specific traits and phenology, affect the distribution and potential roles of fish carrion in stream food webs. [ABSTRACT FROM AUTHOR]

Dams and reservoirs present diverse hazards for riverine fishes, including slowed migration, reduced or blocked access to essential habitats, and direct and delayed mortality risks. Many of these hazards are evident for Pacific Lamprey Entosphenus tridentatus in the heavily dammed Columbia River basin, where the species' distribution and abundance has sharply declined. In a 3‐year study, we used acoustic telemetry to investigate behavior and apparent survival of 784 adult Pacific Lampreys in Columbia River reservoirs and turbulent dam tailraces, two environments where previous monitoring efforts have been somewhat ineffectual. We released Pacific Lampreys upstream and downstream from Bonneville Dam to test whether Pacific Lamprey passage at one dam negatively affected upstream dam and reservoir passage metrics (i.e., delayed effects on migration rate or reach passage success) and whether upstream‐released groups migrated further than their downstream‐released counterparts. Overall, results showed that Pacific Lampreys migrated very rapidly (median rates = 50–62 km/d) in reservoir reaches and slowly (1–3 km/d) in reaches with tailraces or fishways. Pacific Lampreys also had much higher passage success in reservoir reaches (reach × year estimates = 0.93–0.99) than in reaches with tailraces or fishways (most estimates = 0.58–0.82). We found little statistical evidence for negative delayed effects of dam passage. Pacific Lampreys released in the Bonneville forebay were far more likely to pass upstream dams (~26–57%) than were those released in the Bonneville tailrace (~20–36%). We conclude that tailraces and fishways constrained the upstream distribution of adult Pacific Lampreys, that reservoirs were not associated with high mortality during active upstream migration, and that translocation past individual dams can increase the upstream migration distance of individuals and population distribution. Areas of continuing uncertainty include behavior and survival during overwintering (i.e., prespawn holding) and the potential delayed effects of tailrace and fishway passage on Pacific Lamprey fitness. [ABSTRACT FROM AUTHOR]

Physiological condition (hereafter shortened to "condition") influences survival, spawning schedules, and reproductive effort in salmonids. In iteroparous females, the effects of first spawning on condition could result in trade‐offs with future reproduction, mediated by postspawning survival, repeat spawning schedule (i.e., consecutive or skip spawning), or reproductive effort. However, which aspects of condition affect these outcomes and when they are sensitive to condition are not well understood. These issues were examined in highly energy‐depleted hatchery‐origin female summer steelhead Oncorhynchus mykiss that were undergoing postspawning reconditioning in captivity. Measures of condition and reproductive characteristics (i.e., fecundity, egg size, and total egg mass [TEM]) at first spawning were examined for their effects on postspawning survival and future spawning schedules, and condition was tracked during reconditioning to examine effects on reproductive characteristics at repeat spawning. The levels of plasma osmolality and triglycerides measured at first spawning were positively correlated with survival probability, suggesting that survival depends on the ability to maintain homeostasis and access stored energy. Surprisingly, size‐standardized TEM measured at first spawning was positively correlated with the probability of consecutive spawning, providing no support for the hypothesized trade‐off between current and future reproduction. This finding instead suggests that both first‐spawning reproductive effort and consecutive spawning may be influenced by condition at earlier points. Plasma triglycerides and growth rates at sampling points 10–20 weeks after first spawning were strongly correlated with size‐standardized egg size and TEM at consecutive spawning, suggesting that reproductive effort and its allocation to egg size and fecundity depend on energetic status during early oogenesis. These results indicate that condition influences survival, repeat spawning schedules, and reproductive characteristics in female steelhead up to a year or more before repeat spawning. If more broadly applicable, these relationships could provide insight into the mechanisms that link environmental conditions with reproductive characteristics in salmonids and other species. [ABSTRACT FROM AUTHOR]

Movement behaviors are central to ecology and conservation. Movement sensing technologies can monitor behaviors that are otherwise difficult to observe under field conditions and may enhance the ability to quantify behaviors at the population scale. We monitored steelhead trout (Oncorhynchus mykiss) spawning behaviors in a seminatural enclosure using accelerometer telemetry tags while simultaneously observing behaviors with underwater cameras. Behavioral assignments from visual observations were compared to acceleration histories to develop assignment criteria for acceleration data, including for a key behavior (oviposition). Behavioral events independently classified using acceleration data prior to reviewing video were compared to video scoring and 97% of holding behaviors, 93% of digging behaviors, and 86% of oviposition/covering behaviors were correctly assigned using acceleration data alone. We applied the method to at‐liberty steelhead in spawning tributaries. Acceleration records revealed putative spawning and oviposition in at‐liberty female steelhead, and time budgets for at‐liberty steelhead were similar to those monitored within enclosures. The use of similar movement sensing tags and classification approaches offers a method for monitoring movement behavior, activity budgets, and habitat use in a broad array of aquatic and terrestrial taxa, and may be especially useful when behaviors are cryptic. [ABSTRACT FROM AUTHOR]

Passage facilities at dams must accommodate a broad array of aquatic species to achieve full river connectivity. In an attempt to improve adult Pacific lamprey (Entosphenus tridentatus) passage, fishway entrance modifications were made at a large dam on the Columbia River in northwestern USA. The modifications consisted of a variable-width entrance weir and flow disrupters to create heterogeneity in water velocities near the bottom, without affecting attraction flows for adult salmonids (Oncorhynchus spp.) or alosids (Alosa sapidissima). Additionally, a lamprey passage structure (LPS) was installed to provide a lamprey-specific route from tailrace to forebay elevation (31 m). Passive integrated transponders and radio transmitters were used to monitor both Pacific lamprey and Chinook salmon (O. tshawytscha) movements. Fish use of the modified entrance was compared to that at a similar, but unmodified entrance before and after modifications. The entrance modifications resulted in increased velocity heterogeneity, but no measurable improvement in entrance efficiencies for lamprey or salmon. Lamprey successfully ascended the LPS, with annual counts ranging from 48 in 2010 to 3,851 in 2016 (0.2–8.9% of lamprey counted at the dam). Radiotelemetry indicated that tagged lamprey resumed upstream passage after LPS use and travelled at rates similar to those that used traditional fishway routes. [ABSTRACT FROM AUTHOR]

The artificial propagation and release of individuals from non‐local populations is a widespread practice that can threaten the genetic integrity of native, locally adapted populations, because of domestication effects from the artificial rearing environments and inter‐breeding with the local populations. Introgressive hybridization was examined in a threatened population of anadromous Oncorhynchus mykiss (Walbaum, 1792) (winter‐run steelhead) in the Willamette Basin, Oregon. Non‐local, hatchery‐reared, summer‐run steelhead are released annually into the basin as mitigation for the impact of numerous dams.Sixteen microsatellite loci were used to detect introgression in adult steelhead of natural origin migrating into the basin before spawning during 2013 and 2014. Bayesian clustering analysis (structure) was used to identify the level of admixture in the population and to assign individuals to clusters.The Bayesian clustering analysis indicated that there are most likely two populations (or clusters) in the study area: a native, coastal, winter‐run steelhead population and a non‐local, summer‐run steelhead population that was derived from artificial crosses between summer‐run coastal and interior redband populations.Introgressive hybridization was detected in 26.4% of the natural‐origin adult steelhead. First‐generation (F1) hybrids were estimated as 4.9–10.1% of the natural‐origin adult steelhead. Hybrids backcrossed to the native, coastal, winter‐run steelhead were nine times more numerous than backcrosses to the hatchery, summer‐run steelhead. The timing of upstream migration was significantly different between the native, winter steelhead and the F1 hybrids.Low numbers of summer steelhead and back‐cross summer‐run hybrids were identified in the natural‐origin population, consistent with the reduced fitness of hatchery‐reared summer steelhead in natural environments. Conservation actions that protect native populations from hatchery fish include altering stocking practices (such as integrated management or sterility), and protecting the remaining intact populations by designating genetic preserves and preventing the release of hatchery‐origin or hybrid steelhead into these areas. [ABSTRACT FROM AUTHOR]

Trap-and-haul is a mitigation strategy at many hydropower dams lacking upstream fish-passage facilities, and protocols are needed to maximise its effectiveness. We used biotelemetry to assess the potential benefits of releasing transported adult Chinook salmon (Oncorhynchus tshawytscha) into a cold-water reservoir v. a relatively warm-water tributary before spawning. Over 5 years, we released 160 salmon into Foster Reservoir (Oregon, USA) and another 102 into the South Santiam River near historical salmon spawning areas further upstream. In total, 70% of reservoir-released salmon entered an upriver tributary after spending a median of 3–95 days annually in the reservoir. Data recovered from 61 archival temperature loggers indicated that salmon were ~3–6°C cooler per day in the reservoir than in the river. We estimated that cumulative exposure of reservoir-released fish was reduced by 64 degree days, on average (range = –129 to 392), relative to river-released fish. Release into the reservoir was not risk free; 14% of all reservoir-released fish fell back downstream v. 1% of river-released fish. We conclude that reduced transport distance, reduced thermal exposure and potential survival benefits of releasing salmon into reservoirs should be weighed against risks of factors such as fallback and homing errors. Trap-and-haul of adult salmon is a conservation strategy in regulated rivers, but better protocols are needed to ensure effectiveness. We demonstrated that Chinook salmon released into a cold-water reservoir had lower thermal exposure than did salmon released into a warm-water tributary where prespawn mortality has been episodically high. The strategy may be effective in dammed rivers with stressful water temperatures. [ABSTRACT FROM AUTHOR]

Coho Salmon Oncorhynchus kisutch were historically absent from a major Columbia River subbasin, the upper Willamette River (UWR), until a fishway was installed at Willamette Falls and a sustained stocking program was implemented in the 1950s. Despite decades of stocking from three diverse source populations (early run, late run, and coastal Coho Salmon) during the second half of the twentieth century, adult abundance above the falls was less than 1,000 annually during the 1990s. A recent surge (>25,000 adults in 2009) has raised concerns about potential interactions with two native anadromous salmonids listed under the U.S. Endangered Species Act: UWR winter‐run steelhead O. mykiss and UWR spring‐run Chinook Salmon O. tshawytscha. We analyzed Coho Salmon stocking records and estimates of abundance from 1954–2017 to summarize population history, demographics, and adult phenology. We also characterized current Coho Salmon distribution using radiotelemetry (n = 219 adults in 2014) and evaluated potential mechanisms associated with changes in adult abundance. We identified a shift in adult migration timing over the time series that was consistent with an increase in late‐run traits and environmental changes affecting migration cues. The distribution of radio‐tagged adults among UWR subbasins was only weakly correlated with past stocking efforts, suggesting that habitat conditions, stocked phenotype, adaptation and range expansion by descendants of the relict stocked populations, or colonization from regional source populations strongly influenced current subpopulation abundance. Annual counts of returning UWR Coho Salmon were positively correlated with counts of Columbia River Coho salmon, suggesting a shared response to freshwater habitat or ocean conditions. Regardless of the underlying mechanisms affecting UWR Coho Salmon distribution and population size, the results illustrate the complex dynamics between changing landscapes and migration corridors, the introduction of nonnative species for harvest management goals, and the potential for nonnative fish to affect the conservation of native populations. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: We conducted a field experiment to test the hypothesis that intragastric radio‐tagging contributed to increased prespawn mortality (PSM) of adult Chinook Salmon Oncorhynchus tshawytscha after collection and transport to spawning sites above high‐head hydroelectric dams. We assessed PSM rates of 970 wild and hatchery Chinook Salmon collected during trap‐and‐haul operations that were released untagged, tagged with passive integrated transponder (PIT) tags only, or double tagged with PIT tags and radio transmitters, and then recovered as carcasses in two Willamette River, Oregon, tributaries from 2009 to 2015. Results revealed no evidence that PSM rates were higher in PIT‐tagged samples than in untagged (but not unhandled) control samples. The PSM rates in double‐tagged samples were variable among years and between locations and indicated that radio‐tagging effects were absent or small in effect size, on average, within each population. While we did not detect a consistent negative double‐tagging effect across locations and years, results suggest that the potential for radio‐tagging effects should be incorporated in study planning and design. We recommend that researchers use experimental designs that include control groups for directly evaluating tagging and handling effects on study outcomes. [ABSTRACT FROM AUTHOR]

Abstract: 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. [ABSTRACT FROM AUTHOR]

Pacific lamprey (Entosphenus tridentatus) is an anadromous species in an ancient lineage of jawless fishes. The species is native to the North Pacific and its marine-accessible freshwater rivers and streams. Pacific lamprey are understudied relative to other anadromous fishes and has severely declined in abundance throughout the Columbia River Basin. Indigenous people of the Snake and Columbia River Basins have long recognized the ecological role and value of lamprey through their spiritual and cultural practices connected to Pacific lamprey. The combined effects of poor passage at dams, historic and continued habitat degradation, and altered marine host conditions have contributed to the observed decline in abundance and distribution. The unique characteristics and management history have placed Pacific lamprey in a legal and cultural grey area and provide a useful foil to Pacific salmon in considering protections for migratory fish. Here we provide a review of legal protections and recovery actions throughout the Columbia River Basin, including an analysis of the Fish and Wildlife Service's 2004 denial of a petition to list Pacific lamprey under the Endangered Species Act. The current patchwork of measures fails to provide integrated protections across the life history of the species. This stems from a complex lifecycle spanning dozens of local, state, tribal, federal, and international jurisdictions as well as a cultural legacy of lamprey being considered "trash fish" by western society and early fishery managers. However, recent shifts in perceptions about the ecological value of the species and increased co-management of anadromous species within the Columbia River Basin have elevated the species as a management priority. Continued efforts to conserve and recover Pacific lamprey pose a complex and honorable challenge for fisheries managers within the Columbia River Basin. [ABSTRACT FROM AUTHOR]

Fish passage systems (fishways) have become the most common mitigation tool for improving the connectivity of migratory fish populations in ecosystems with barriers to movement. Because fishways often have high-velocity and high-turbulence environments, fish should seek low-energy movement paths during passage. We tested this hypothesis by analyzing the swimming paths of 90 adult Pacific lamprey ( Entosphenus tridentatus ) in response to hydraulic conditions when passing a vertical-slot weir in an experimental fishway. Varying hydraulic conditions were achieved by manipulating three variables: water velocity (1.2, 1.8, 2.4 m/s), vertical-slot length (0.33 m, 0.66 m, 1.00 m), and presence or absence of a turbulence-inducing structure. Turbulence parameters, such as turbulent kinetic energy ( TKE ), were quantified using an Acoustic Doppler Velocimeter (ADV). Pacific lamprey exhibited context-dependent behaviors in response to turbulence whereby lamprey were more likely to move towards areas of lower turbulence along their swimming paths, but only as the surrounding turbulence within the vertical-slot increased. In contrast, when the surrounding turbulence within the vertical-slot was low, Pacific lamprey became more likely to move towards areas of higher turbulence. The ‘turbulence-avoidance’ behaviors likely allowed passage of the hydraulic obstacle by reducing energy expenditure or physiological stress, while the ‘turbulence-attraction’ behaviors may have resulted from lamprey using turbulence as a mechanism for upstream orientation. Overall, our results provide new insight into how fish may use turbulence as an important sensory modality for perceiving the aquatic environment. [ABSTRACT FROM AUTHOR]