Spatiotemporal variation in habitat quality and quantity impacts individual fish energetics by influencing growth, energy storage, and survival, ultimately shaping population dynamics. However, few studies have explicitly linked individual energetic condition to habitat variation across both space and time. In two studies, we investigated the influence of variation in freshwater habitat characteristics (September 2020) and season (July 2022 to April 2023) on both physiological (e.g., percent lipid, percent protein, and energy density) and morphological (e.g., relative condition factor) metrics of juvenile coho salmon energetic condition in interior British Columbia, Canada. Physiological metrics were associated with spatial and temporal variation in habitat. Among sites, higher percent lipid was associated with lower water temperature and higher energy density with elevated stream nutrient concentrations. Across seasons, energetic condition declined over both summer and winter. Post-winter percent lipid and energy density values converged on proposed survival thresholds. Collectively, this research demonstrates the utility of physiological energetic condition metrics as tools for quantifying how habitat changes affect juvenile salmon energetic condition, improving evaluations of habitat protection and restoration actions.

Abstract Climate change is threatening ecologically and culturally important species. For species with broad ranges and complex life cycles, such as migratory Pacific salmon (Oncorhynchus spp.), climate exposure may vary across space and diverse life history strategies. Here, we quantify climate exposure and adaptive capacity across the North American range and remarkable phenological diversity of Chinook salmon (O. tshawytscha). We compiled data on adult freshwater migration timing and its environmental covariates for 295 populations of Chinook salmon spanning 29 degrees of latitude from California to Alaska. We linked this migration timing data to recent (1990s) and future (2040s) water temperatures to quantify thermal exposure during each population's timing of entrance to freshwater. At northern latitudes, Chinook migration timing was compressed to 3 months during the summer, while at southern latitudes, migration occurred across months before and after stressful peak summer water temperatures. Earlier migration timing was associated with longer migration distances and greater elevations gained. Thermal exposure was controlled by latitude and run‐timing, with lower latitude and summer and fall runs being most exposed to potentially harmful temperatures both now and into the future. However, potentially harmful climate exposure was predicted to increase the most in mid‐latitude populations (~45° to 55°) that have not yet adapted to migrate before and after peak summer temperatures. If Chinook salmon phenology were to keep pace with projected climate warming by the 2040s, the majority (75%) of populations would need to shift their migration timing earlier in the year, pulling their migration farther apart from their fall spawning phenology. Collectively, these findings showcase how latitude and life history diversity influence climate change risk and indicate the importance of preserving existing migration timing diversity and adaptive capacity across the broad range of a migratory species.

Cumulative effects of land-use change and climate change are leading to biodiversity decline globally. Spatial analyses of cumulative pressures that distill complexity and provide actionable information for the management of cumulative pressures on vulnerable species are needed. For example, many populations of Pacific salmon are struggling across their vast range because of their exposure to myriad land-use and climate change symptoms. Understanding the spatial distribution of cumulative pressures is of importance for policy makers, watershed, fisheries and conservation managers to identify pathways forward for the diverse set of challenges facing salmon. We characterize the spatial patterns of multiple cumulative effect pressures, examine pressure co-occurrence and observe how the spatial distribution and co-occurrence of cumulative effect pressures links to salmon population status and overlaps with spawning habitats. To do so, we used 17 indicator variables representing forest disturbances, urbanization, mining, local geography and climate change in a k-means unsupervised classification algorithm. Our results show eight distinct watershed archetypes (urban, mid-elevation remote, coastal forestry, interior uppers, developed interior, mining interior, mountainous, remote coast) characterized by unique stressor profiles distributed throughout the study area. Certain species of Pacific salmon were disproportionately represented in specific watershed archetypes. Further, archetypes with greater disturbance contained fewer salmon populations assessed as good status and more populations with poor status. Practical implication. Salmon watershed archetypes can help inform the distinct suites of management actions required to mitigate the impacts of cumulative effects on these ecologically, culturally and economically important species.

Pacific salmon (Oncorhynchus spp.) and their roles in the ecosystems, cultures and economies of the Pacific Northwest face a convergence of threats, most of which began or intensified during the onset of settler colonialism in North America. This Review discusses how these threats to wild Pacific salmon and their ecosystems cause inequities for the Indigenous Peoples who rely on them. We consider four previously identified forms of equity (recognitional, procedural, distributional and contextual) and introduce an additional form of equity (epistemic) specific to the injustices perpetrated against Indigenous Peoples and their knowledge systems. We highlight how cumulative effects of factors driven by colonial mismanagement, including, among others, mixed-stock marine fisheries, climate change, invasive species, land use, pollution and aquaculture are affecting wild Pacific salmon populations, while resulting in cumulative injustices for Indigenous communities who have stewarded salmon for millennia (the Salmon Peoples). We identify opportunities for transformative justice through the governance of salmon and their ecosystems, to realize equitable conservation practices that honour ecological integrity and social justice. Pacific salmon face mounting threats rooted in colonialism, driving inequities for Indigenous Salmon Peoples. This Review introduces the concept of ‘cumulative injustices’ and examines salmon systems through five equity dimensions, identifying opportunities for transformative change that honours ecological integrity and justice in Canada and the USA.

Wildfires, unplanned fires that start and spread under the influence of weather and fuel composition, are increasing in frequency, duration, and severity across North America. While wildfires are one component of wildland fire, a broader natural process in many ecosystems, their changing behavior poses growing ecological and management challenges. Although wildfire is widely recognized as an important disturbance, empirical research quantifying its impacts on freshwater ecosystems remains limited and fragmented. As a result, our understanding of how wildfire affects imperiled freshwater systems remains underdeveloped. The objective of this review was to synthesize the existing empirical literature and identify key knowledge gaps to guide future research on wildfire-freshwater interactions across both biotic and abiotic components. At the biological scale, uncertainties remain around species- and community-level responses (e.g., direct and indirect effects on biota). Freshwater habitat dimensions should also be the focus of further research, including alterations to physical structure (e.g., vegetation) and physicochemical conditions (e.g., temperature). From a management perspective, critical questions relate to fire-informed restoration (e.g., specialized techniques, role of managed burns) and strategies for enhancing ecosystem resilience (e.g., identifying relevant indicators, links to watershed health). Understanding how land-use change (e.g., forestry) and climate change interact to influence wildfire regimes and generate cumulative effects across landscapes is also essential in this new wildfire reality. To advance research and practice, we recommend comprehensive monitoring, standardization of methods and indicators, recognition of the role of cultural and prescribed burns, meaningful knowledge co-production, and bridging the gap between scientific knowledge and management action.

ABSTRACT The dual crises of climate change and biodiversity loss continue despite overwhelming scientific evidence of their impacts on human well‐being and planetary health. Those of us working in the fields of conservation and ecology are acutely aware that current efforts to avert these crises are profoundly inadequate. But how are we, as professionals working in these fields, responding? We engage in many different activities from generating knowledge and educating students to communicating research findings. Some of us work to implement science‐based evidence and advocate for policy change. A few of us engage in activism. In this perspective, we explore how to increase our impact by re‐prioritizing how we spend our time on various activities and focus our efforts on actions most likely to lead to positive change. We offer an exercise to self‐reflect and identify pathways to increase our impact. The escalating crises demand an urgent re‐think from us all in how we currently spend our time.

Canada’s Wild Salmon Policy (WSP) offers a framework for conserving the genetic and geographic diversity of wild Pacific salmon. A cornerstone of the Policy is the annual assessment of endangered status for each Conservation Unit (CU). We evaluated the extent of monitoring as a foundation for WSP implementation and its goal of safeguarding salmon diversity. Publicly-reported annual counts of spawning populations have declined by 32% since the Policy’s release, driven largely by reductions in high-quality surveys. Synchrony among spawning populations within CUs is low and variable, underscoring the limitations of relying on indicator populations to represent CU-level trends. Nearly half of Canada’s Pacific salmon CUs with publicly-available data currently lack sufficient information to assess status using the recent generational metric, with 27 additional CUs having insufficient data since the Policy’s release. This erosion of population-level spawner data compromises the ability to detect biological change and inform timely conservation responses. Rebuilding broad and representative monitoring programs is essential to fulfill the WSP’s core commitment to conserving wild salmon diversity.

River floodplains are dynamic mosaics of aquatic and riparian habitats maintained by flow regimes and sediment processes, but these floodplains may be rapidly shifting with climate change. Specifically, previous work has highlighted that glacier retreat can be associated with river channel and floodplain change. Within a large and glacially influenced watershed, the Taku Watershed of northwestern British Columbia and southeastern Alaska, we used remote sensing and Geographic Information System (GIS) to quantify four decades of annual floodplain habitat composition and river channel patterns in 16 subwatersheds that naturally varied in their glacier coverage and other landscape (e.g., floodplain elevation, slope) and climate variables (e.g., temperature, precipitation). We discovered rapid development of floodplain vegetation and increased habitat stability in subwatersheds with higher glacial coverage, and a lack of directional change in other subwatersheds. Floodplain vegetation coverage almost doubled over 38 years in subwatersheds with the highest glacier coverage. Focal analyses revealed that river channel structure also shifted in glacierized subwatersheds, with decreases in habitat turnover rate, water occupancy and some evidence for decreasing levels of channel braiding. A large landslide (1.5 km runout, 130 ha) during the study period caused a local disturbance to one of the floodplains, but with little immediate broader impacts at the scale of the entire floodplain. Collectively, climate change and associated glacier retreat are leading to the rapid transformation of floodplain ecosystems, with major implications for the habitat of important species such as migratory salmon.

Restoring the relationships, rights, and responsibilities of Indigenous Peoples to their salmon kin is central to a sustainable and just future with Pacific salmon, particularly as Nations lead the restoration of freshwater salmon habitat in their territories. As a group of Indigenous and non-Indigenous researchers from across British Columbia, we come together in a respectful and transparent way to uphold ancestral Indigenous Pacific salmon stream caretaking knowledge, longstanding Indigenous rights and relationships to land and waters, and our joint responsibilities to care for these watersheds. To do this, we begin by describing traditional governance systems that house Indigenous salmon stream caretaking practices. Through a literature review and conversations with co-authors, we then describe eight Indigenous salmon stream caretaking practices. Finally, we share three contemporary focal stories of Indigenous salmon restoration projects that uphold ancestral knowledge; “Syilx sockeye restoration”, “səlilwətaɬ (Tsleil-Waututh) led salmon habitat restoration in xʔə’l̓ilwətaʔɬ (Indian River Watershed)”, and nuučaanuɫ (Nuu-chah-nulth) Peoples and salmon: responsive methods through steadfast lifeways’. We present stream caretaking knowledge and the focal stories as learning opportunities that may guide future human-salmon relationships and restoration.

Freshwater fish such as juvenile salmon often rely on dynamic and diverse habitats such as wetlands. Although juvenile salmon wetland use is well documented, their use of freshwater wetlands in large river networks that vary in isolation and connection is not well known. We studied juvenile coho salmon use of three wetland sites along the North Thompson River, British Columbia, Canada, from May 2021 to October 2023 to understand how seasonal variation in wetland connectivity and water quality (temperature and dissolved oxygen) influence juvenile coho salmon habitat use. We used monthly mark–recapture sampling to estimate juvenile coho salmon abundance and density. Seasonal abundance and growth of juvenile coho salmon in wetlands were intertwined with connectivity and abiotic conditions. Age-0 juvenile coho salmon were recruited to wetlands during high spring flows and used wetland habitats year-round. Periods of high density and low oxygen were associated with lower growth and abundance. Our study also provides information on the timing of juvenile coho salmon use of wetland habitats, which can be used to inform habitat managers of times of year that pose the greatest risk and benefits to these fish.

Objective Recreational fisheries are complex social-ecological systems, with interactions and feedbacks across local and regional scales and among individual fish, anglers, and managers. Understanding the link between true fish abundance and angler catch per unit effort (CPUE) is crucial to inform management decisions in these systems, especially in the absence of independent monitoring data. For instance, the relationship between fish abundance and CPUE could be linear or nonlinear, such as a hyperstable relationship, which occurs when CPUE remains high even as population abundance declines. We investigated the relationship between fisheries-independent abundance and CPUE in steelhead Oncorhynchus mykiss and evaluated the extent to which hyperstability may obscure underlying population declines.Methods We analyzed the relationship between steelhead abundance and CPUE in 14 streams across the province of British Columbia, Canada. To explore the impact of hyperstability on our capacity to detect changes in abundance, we simulated three scenarios of steelhead decline, comparing the rate of change in CPUE versus abundance.Results Our findings revealed sweeping patterns of hyperstability, indicating that when populations are depressed, CPUE does not decrease as rapidly as abundance. Additionally, we found that the magnitude of CPUE overestimation varied with the extent of population decline. For example, when the population declined by 50%, CPUE decreased by only 40%, representing a 28% overestimation of remaining abundance. This disparity increased in more extreme scenarios of decline.Conclusions Our findings underscore that catch data can mask fish population declines and highlight the need for improved fish population monitoring in recreational fisheries. Limited fisheries-independent data exist for steelhead; therefore catch data often serve as a key source of information for many stocks. Due to hyperstability, catch rates may remain high even as fish numbers fall, masking true population declines and complicating conservation efforts.

The cumulative effects of climate change and human activities pose major challenges for environmental management, a problem exemplified by Pacific salmon ecosystems. We offer an integrative treatment of both the science and policy levers of cumulative effects and reveal the sheer complexity of effective governance of salmon ecosystems in British Columbia, Canada. We then present and examine a hypothetical conceptualization of cumulative effects and their governance in salmon ecosystems to highlight several barriers and opportunities. We find that the progressive degradation of many salmon habitats appears to be enabled by the current policy approach through scarce monitoring, ineffective assessment, lack of legal limits, and isolated decision-making. At the same time, climate change magnifies the urgency of effective management as human activities act cumulatively with climate change impacts. However, our synthesis also highlights opportunities with existing but underused policy levers within Crown and Indigenous governance, as well as local co-governance arrangements, that could improve salmon ecosystem management. Although positive steps have been made toward managing several stressors, the current challenges facing Pacific salmon underscore the need for a fundamental shift in the treatment of cumulative effects.

Objective Managing data-limited populations is a challenge to the sustainability of fisheries globally. Meta-analytic approaches, where insights from data-rich populations are drawn on to inform data-limited ones, along with the use of habitat-based information, have each been proposed as ways to overcome data-limited assessment challenges, but the two approaches have rarely been combined. Sockeye Salmon Oncorhynchus nerka spawn and rear in many remote coastal watersheds of British Columbia, Canada, challenging comprehensive population assessments. Estimating conservation and management reference points for such populations is particularly relevant given their importance to Indigenous and commercial fisheries. Most Sockeye Salmon have obligate lake-rearing as juveniles, and total abundance is typically limited by production in nursery lakes. Although methods have been developed to estimate population capacity based on the photosynthetic rate of nursery lakes and lake area or volume, they have not yet been widely incorporated into spawner-recruitment analyses.Methods We tested the value of combining these lake-based capacity estimates with various hierarchical structures in spawner-recruitment analyses to assess population status using a set of Bayesian spawner-recruitment models for 69 populations across coastal British Columbia, many of which were data limited.Results Our analysis revealed regional variation in the population productivity of Sockeye Salmon, with coastal populations exhibiting slightly lower mean productivity than those in interior watersheds. Hierarchical spawner-recruitment models with and without informative lake habitat-based priors greatly improved predictive ability across all populations.Conclusions These findings reveal opportunities to integrate spatial analyses of habitat characteristics with population models to inform the conservation and management of exploited species and their natal habitats, particularly where populations are data limited. Evaluating the status of data limited fish populations to inform fisheries management is a core challenge for the sustainability of fisheries around the world. In Canada's remote North and Central Coast region, hundreds of salmon populations are lacking in formal assessment to define management benchmarks. One opportunity to improve the available information about population status and inform sustainable fisheries management is to integrate habitat-based insights with traditional spawner-recruit modeling to estimate stock status and management benchmarks for data-limited populations. Most Sockeye Salmon rear in freshwater lakes for 1-2 years prior to their seaward migration, and maximum population sizes are limited by the size and productivity of their rearing lake. Using a Bayesian-hierarchical modeling approach, we integrated information on lake size and productivity into a Ricker spawner-recruit model as prior information for 69 Sockeye Salmon populations on the remote North and Central Coast of British Columbia. We further evaluated the benefits incorporating regional biogeographic differences in productivity-the number of offspring produced at low spawner abundance-into models that we used to estimate the status of Sockeye Salmon populations. Overall, we found that this Bayesian-hierarchical approach greatly reduced uncertainty in the estimated population parameters that are used to inform assessments of stock status, particularly for the most data-limited populations that we evaluated.

Climate change and local pressures are eroding the health and performance of many watersheds and their freshwater ecosystems, pushing these complex social-ecological systems to the boundaries of their safe operating space. Here, we offer a synthetic perspective on the downscaled application of the safe operating space concept to inform the stewardship of watersheds in this time of rapid climate change, with particular focus on watersheds that support coldwater migratory fishes such as Pacific salmon. First, we review the safe operating space concept as it applies to salmon watersheds as social-ecological systems. Salmon watersheds, and the benefits they provide for diverse peoples, are under enormous cumulative pressure from climate change as well as local activities such as forestry, urbanisation, mining and agriculture. We identify four general syndromes of dual local and climate pressures. For example, local pressures, such as the removal of riparian vegetation that shades streams, can exacerbate climate warming of water temperatures. Furthermore, extractive industries can damage or destroy future habitats and thus erode adaptive capacity. As an illustrative example of how the safe operating space concept can be operationalised, we assess alternative plausible watershed futures of land use and climate change scenarios and salmon performance. Collectively, this work showcases tangible options for local management to help give salmon watersheds the time and space to cope with climate change. More broadly, while there is a global need to address climate change, local watershed management is a key component of pathways towards freshwater sustainability and their services for humanity.

The impacts of climate change are widespread and threaten natural systems globally. Yet, within regions, heterogeneous physical landscapes can differentially filter climate, leading to local response diversity. For example, it is possible that while freshwater lakes are sensitive to climate change, they may exhibit a diversity of thermal responses owing to their unique morphology, which in turn can differentially affect the growth and survival of vulnerable biota such as fishes. In particular, salmonids are cold-water fishes with complex life histories shaped by diverse freshwater habitats that are sensitive to warming temperatures. Here we examine the influence of habitat on the growth of sockeye salmon ( Oncorhynchus nerka ) in nursery lakes of Canada's Skeena River watershed over a century of change in regional temperature and intraspecific competition. We found that freshwater growth has generally increased over the last century. While growth tended to be higher in years with relatively higher summer air temperatures (a proxy for lake temperature), long-term increases in growth appear largely influenced by reduced competition. However, habitat played an important role in modulating the effect of high temperature. Specifically, growth was positively associated with rising temperatures in relatively deep (>50 m) nursery lakes, whereas warmer temperatures were not associated with a change in growth for fish among shallow lakes. The influence of temperature on growth also was modulated by glacier extent whereby the growth of fish from lakes situated in watersheds with little (i.e., <5%) glacier cover increased with rising temperatures, but decreased with rising temperatures for fish in lakes within more glaciated watersheds. Maintaining the integrity of an array of freshwater habitats—and the processes that generate and maintain them—will help foster a diverse climate-response portfolio for important fish species, which in turn can ensure that salmon watersheds are resilient to future environmental change.

Abstract Forestry is pervasive across temperate North America and may influence aquatic environmental conditions such as flows and temperatures, as well as important species such as Pacific salmon (Oncorhynchus spp.). While there have been many large‐scale forestry experiments using paired catchment designs, these studies have yet to be quantitatively synthesized. Thus, it remains unclear whether forestry impacts are consistent, context‐dependent or unpredictable. This study aims to quantitatively synthesize forestry impacts on streamflow and temperature, through a systematic review and synthesis of paired catchment studies across the range of Pacific salmon. Specifically, we investigated whether generalizable relationships exist between forestry intensity (percent watershed harvested) and impacts to streamflow and temperature. We also examined whether watershed features (climate, hydrology and lithology) and harvest method mediated forestry impacts. We extracted information from 35 unique paired‐catchments from California to Alaska. Forestry had strong impacts on peak and low flows and maximum summer water temperatures, but responses were quite variable. Across all catchments, forestry elevated peak flows ~20% (n = 31 catchments), reduced low flows ~25% (n = 13 catchments) and increased maximum summer temperatures ~15% (n = 35 catchments) on average. However, these impacts were variable and were not predictable based on forestry intensity, thus broader stressor–response relationships were not supported. Forestry impacts on peak flows and maximum summer temperatures varied spatially. Peak flow impacts increased with northward latitude and temperature impacts decreased with eastward longitude. However, the magnitude of impacts were unrelated to other watershed attributes, which included climate (precipitation and aridity), rain versus snow hydrology, elevation and bedrock lithology. Harvest method and riparian buffer presence also had no detected effects on forestry impacts across studies and statistical models explained a low proportion of variation overall. Collectively, our results indicate that forestry can have substantial impacts on key environmental conditions; however, the magnitude of impact was variable and could not be clearly linked to easily measured watershed characteristics. This implies that forestry impacts may not be broadly predictable. Probabilistic risk models based on distributions of potential impacts may therefore be more useful for watershed management in data‐poor situations.

The value of estuaries as nursery habitat for juvenile anadromous salmon is likely variable across estuaries and species. Here, we compiled published empirical data on juvenile salmon estuarine growth and residency. We aimed to quantify the range and variability of these aspects for five species of Pacific salmon across estuaries, methodologies, and life histories. The majority of studies focused on Chinook and coho salmon, largely from their southern range. While there is some evidence of higher growth in wild-origin fish relative to hatchery-origin fish, the wide range of metrics employed made identification of trends among life histories challenging, and unification of reporting could strengthen future research. Different salmon life histories exhibited different residencies, with natural-origin subyearling coho exhibiting the longest mean residency (similar to 3 months) and 1+ sockeye salmon exhibiting the shortest (3.7 days). Across life histories, hatchery fish exhibited much shorter estuary residencies than wild fish. Collectively, our review highlights key patterns in salmon estuary ecology, identifies knowledge gaps, and lays the foundation for future studies to quantify the importance of estuaries for specific salmon.