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The revised Fisheries Act requires that Limit Reference Points (LRPs) be identifed for all major fsh stocks. For Pacifc salmon, major fsh stocks are represented by stock management units (SMUs). An SMU is composed of one or more salmon conservation units (CUs), which are the assessment units under the Wild Salmon Policy, WSP. We introduce methods to estimate LRPs at the SMU level that integrate statuses derived under the WSP at the CU level. We demonstrate and evaluate the LRPs for three case study SMUs: Interior Fraser Coho (Oncorhynchus kisutch), West Coast Vancouver Island (WCVI) Chinook (O. tshawytscha), and Inside South Coast Chum (O. keta) - excluding Fraser River. Methods are divided into two categories: CU status-based LRPs and aggregate abundance LRPs. CU status-based LRPs are recommended as the default method, and are based on the proportion of CUs above levels associated with increased risk of extinction (above 'Red' status) under the WSP. Aggregate abundance methods may be used supplementally to meet specifc fsheries management requirements. Aggregate abundance LRPs are subdivided into logistic regression LRPs and projection LRPs. Both types of aggregate abundance LRPs are defned at the SMU-level abundances associated with a desired probabilty of all component CUs being above Red status, but they differ in that logistic regression LRPs are determined directly from historical data while projection LRPs are determined from projections of CU-level population dynamics. We discuss suitability and requirements for the application of the various LRP estimation methods, drawing from the range of data and information availability among the case studies. In general, the application of aggregate abundance LRPs may be limited to SMUs where the CU-level populations covary, as demonstrated for the Interior Fraser Coho case study, and where covariance has not changed over time or, for projection LRPs, those changes can be parameterized. [ABSTRACT FROM AUTHOR]

Limit reference points, LRPs, defne the stock status below which serious harm is expected to occur to a stock. LRPs are required for major fsh stocks, or Stock Management Units (SMUs) that are prescribed by regulation under amendments to the Canadian Fisheries Act (2019). Pacifc salmon are unique among marine fsh stocks due to their high levels of intraspecifc diversity which gives rise to a large range in data availability, considerations, and approaches for assessments and LRP development. In this paper, we identify six principles for developing LRPs for Pacifc salmon that are adapted from principles used more broadly among marine species. One principle unique to Pacifc salmon is that LRPs should be aligned with Canada's Wild Salmon Policy (WSP) objective of preserving biodiversity of salmon at the scale of Conservation Units (CUs), which are nested within SMUs. We developed methods for calculating LRPs, and established guidelines on how to implement them including under which conditions they should or should not be applied. We propose that LRPs be identifed from the proportion of CUs that have status above the Red zone for WSP status assessments, as a default approach. This provides some consistency with status assessments already produced under the WSP, and can inform management decisions for harvest, habitat and hatcheries that often occur at fner, CU scales. To supplement the default approach, we provide LRPs based on metrics of aggregate abundances for the entire SMU, which may be required for fsheries management purposes in some cases. These latter LRPs are derived to have a desired probability of all component CUs being above Red status given an assumed relationship between aggregate abundance and the probability that all CUs will be above Red status. We identify uncertainties associated with each approach, and describe how they can be applied across a range of data types, qualities and quantities. Analyses to support our development of guidelines has been informed by three cases studies: Interior Fraser Coho Salmon Oncorhynchus kisutch, West Coast Vancouver Island Chinook Salmon, O. tshawytscha, and Inside South Coast Chum Salmon, O. keta, excluding the Fraser River. [ABSTRACT FROM AUTHOR]

Models with time-varying parameters are increasingly being considered in the assessment of fish stocks, but their reliability when used to derive biological reference points or benchmarks has not been thoroughly evaluated. Here, we evaluated stock–recruitment models with and without time-varying productivity in a simulation framework for sockeye salmon (Oncorhynchus nerka) under different scenarios of productivity and exploitation. Ignoring trends in productivity led to overestimates of productivity and underestimates of capacity when both exploitation rates and productivity declined over time, resulting in an underestimation on average of benchmarks of biological status. Despite being less biased, time-varying models had relatively poor fit based on AICc and BIC model selection criteria. Our simulation results were compared with empirical analyses of 12 Fraser River sockeye salmon stocks in British Columbia, Canada. Although benchmarks were less biased when based on time-varying models, underlying true benchmarks based on spawner abundances at maximum sustainable yield, SMSY, trend downwards when productivity declines, which may not be aligned with conservation objectives. We conclude with best practices when adapting biological benchmarks to time-varying productivity. [ABSTRACT FROM AUTHOR]

Empirical dynamic modelling (EDM) is becoming an increasingly popular method for understanding the dynamics of ecosystems. It has been applied to laboratory, terrestrial, freshwater and marine systems, used to forecast natural populations and has addressed fundamental ecological questions. Despite its increasing use, we have not found full explanations of EDM in the ecological literature, limiting understanding and reproducibility. Here we expand upon existing work by providing a detailed introduction to EDM. We use three progressively more complex approaches. A short verbal explanation of EDM is then explicitly demonstrated by graphically working through a simple example. We then introduce a full mathematical description of the steps involved. Conceptually, EDM translates a time series of data into a path through a multi‐dimensional space, whose axes are lagged values of the time series. A time step is chosen from which to make a prediction. The state of the system at that time step corresponds to a 'focal point' in the multi‐dimensional space. The set (called the library) of candidate nearest neighbours to the focal point is constructed, to determine the nearest neighbours that are then used to make the prediction. Our mathematical explanation explicitly documents which points in the multi‐dimensional space should not be considered as focal points. We suggest a new option for excluding points from the library that may be useful for short‐term time series that are often found in ecology. We focus on the core simplex and S‐map algorithms of EDM. Our new R package, pbsEDM, enhances understanding (by outputting intermediate calculations), reproduces our results and can be applied to new data. Our work improves the clarity of the inner workings of EDM, a prerequisite for EDM to reach its full potential in ecology and have wide uptake in the provision of advice to managers of natural resources. [ABSTRACT FROM AUTHOR]

Management strategies that track time-varying productivity may better achieve management objectives than those that assume constant productivity. In Canada, biological assessments of Pacific salmon populations use upper and lower benchmarks to delineate three zones of status, green, amber and red, representing increasing probability of extirpation, reduced production, and possible increases in management intervention. Although benchmarks that track changes in productivity based on stock–recruitment relationships have been evaluated in closed-loop simulation models, benchmarks for data-limited populations that do not use recruitment relationships have not. The primary objective of this study was to evaluate the performance of lower benchmarks for data-limited populations derived from a percentile of observed spawner time-series, against those derived from data-intensive methods, using a closed-loop simulation model that included temporal changes in stock productivity. We also evaluated the role of assumptions about metapopulation dynamics and outcome uncertainty (uncertainty from the outcomes of implementing harvest management decisions) on the relative performance of lower benchmarks. Our results suggest caution when applying percentile-based benchmarks to harvest management decision rules due to high probabilities of extirpation especially when productivity is declining and outcomes of management actions are uncertain. We further provide a risk assessment framework for evaluating probabilities of extirpation of candidate benchmarks and possible trade-offs associated with harvest opportunities. [ABSTRACT FROM AUTHOR]

For fisheries with multiple, competing objectives, identifying and applying reference points for management can present difficult trade-offs between long-term biological and shorter-term socioeconomic considerations. The term biological benchmarks is proposed to demarcate zones of population status based on conservation and production considerations. These scientifically derived benchmarks contrast with management reference points that generally require additional shorter-term socioeconomic information best obtained through public consultations. This paper illustrates the distinction between biological benchmarks and management reference points with a case study on Pacific salmon (Oncorhynchus spp.). In Canada, the management and assessment of wild Pacific salmon are guided by a major 2005 conservation policy, which calls for the identification of biological benchmarks to categorize status of demographically isolated populations, and decision-support tools, such as management reference points, to integrate biological information with appropriate social and economic information. In the Fraser River (British Columbia, Canada), the selection of management reference points for sockeye salmon (O. nerka) fisheries explicitly considered trade-offs between the probability of meeting long-term biological objectives on component populations and harvest objectives on population aggregates. Decisions about reference points were made in a consultative process that included extensive stakeholder engagement. Other agencies are urged to distinguish biological benchmarks from management reference points to ensure transparency in the relative influence of biological versus socioeconomic information in decision making. [ABSTRACT FROM PUBLISHER]

Highlights: [•] A probabilistic net can be applied for ecosystem-based management of juvenile coho salmon. [•] Hatchery supplementation may be more effective during favorable ocean conditions. [•] The probabilistic network can be used to identify indicators of juvenile survival. [Copyright &y& Elsevier]

The distribution of individuals among populations and in space may contribute to their resilience under environmental variability. Changes in distribution may indicate the loss of genetically distinct subpopulations, the deterioration of habitat capacity, or both. The distribution of Pacific salmon ( spp.) among spawning locations has recently been recognized as an important component of status assessment by USA and Canadian management agencies, but metrics of spawning distribution have not been rigorously evaluated. We evaluated three metrics of spawning distribution and four sampling designs for their ability to detect simulated contractions in the production of coho salmon (). We simulated population dynamics at 100 sites using a spawner-recruit model that incorporated natural variability in recruitment, age-at-maturity, dispersal, and measurement error in observations of abundance. Sensitivity analyses revealed that high observation error and straying of spawners from their natal streams may mask changes in distribution. Furthermore, monitoring only sites with high spawner abundance, as is often practiced, failed to capture the simulated contraction of production, emphasizing the importance of matching monitoring programs with assessment objectives. [ABSTRACT FROM AUTHOR]

Holt, C. A. 2010. Will depleted populations of Pacific salmon recover under persistent reductions in survival and catastrophic mortality events? – ICES Journal of Marine Science, 67: 2018–2026.Under Canada's Wild Salmon Policy, benchmarks between zones of biological status are required to distinguish populations requiring conservation attention (Red and Amber zones) from those that can be managed for production (Green zone). The recovery of depleted populations (i.e. from Red to Green) will depend in part on the choice of the lower benchmark. At a minimum, that benchmark should be set high enough to allow recovery within an acceptable time-frame in the absence of targeted fishing. Currently, benchmarks are evaluated and selected using simulation models that assess the probability of recovery to spawner abundance associated with the maximum sustainable yield within a specified time-frame. Guided by case examples, the evaluation is extended to include two scenarios of future conditions: persistent reductions in survival rates below the replacement level; and increased frequency of catastrophic mortality (die-off) events. Probabilities of recovery appear to be more sensitive to persistent reductions in survival than to increased probability of die-off events. The current lower benchmarks on spawner abundance and fishing mortality might not be sufficiently precautionary to allow recovery under those conditions. [ABSTRACT FROM PUBLISHER]

Abstract: Rebuilding plans are required by the U.S. Sustainable Fisheries Act (1996) for stocks that are designated to be overfished, including several stocks of groundfish on the U.S. west coast. Despite evidence for climate effects on groundfish recruitment, the analyses that underlie rebuilding plans have not incorporated those effects. We extended the conventional approach used to conduct rebuilding analyses to evaluate the sensitivity of outputs from those analyses to two hypotheses about climate effects on recruitment (temporal autocorrelation due to unknown factors, and reduction in expected recruitment due to a delay in the date of spring transition) for an overfished stock, Pacific ocean perch (Sebastes alutus). We found that catch limits, probabilities of rebuilding to target levels, and times for rebuilding were sensitive to assumptions about recruitment, and those assumptions may have an important influence on management decisions. The Pacific Fisheries Management Council currently makes trade-offs between time for rebuilding and catch limits using outputs of rebuilding analyses combined with social and economic considerations, but in the future, account could also be taken of information on climate effects on recruitment. [Copyright &y& Elsevier]

Fisheries managers usually have multiple options available but are often unclear on how to choose among them owing to uncertainties in biological and management components of fisheries systems. We evaluated the performance of current and possible future assessment and management practices for sockeye salmon (Oncorhynchus nerka) in British Columbia and Alaska by using a computer model that included major biological and management components and their associated uncertainties (interannual variability in recruitment, age-at-maturity, and sex ratio, as well as uncertainty in observations of spawner abundances, forecasts of recruitment, and outcomes from implementing management regulations). One option for management practices that we evaluated was designed to make the forecasting model more realistic by accounting for long-term trends in age-at-maturity. A second option was designed to reduce deviations between management targets and actual or “realized” harvest levels. We found that compared with practices that ignore those sources of uncertainty, the second option produced annual catches that were higher, on average, and less variable over time while maintaining recruitment above critical conservation levels. Contrary to our expectations, the first modification did not result in comparable benefits. Our results demonstrate the value of using simulation models to evaluate potential modifications to Pacific salmon management practices. [ABSTRACT FROM AUTHOR]

In sockeye salmon (Oncorhynchus nerka) fisheries, management targets are rarely achieved exactly, thereby creating uncertainties about outcomes from implementing fishing regulations. Although this type of uncertainty may be large, it is seldom incorporated into simulation models that evaluate management options. One objective of this study was to quantify the deviations that occur between realized and target mortality rates (i.e., the target fraction of adult recruits that die each year during return migration, mostly due to harvesting) in fisheries for sockeye salmon from the Fraser River, British Columbia. We found that for some sockeye stocks, realized mortality rates were higher than targets when recruitment was low (resulting in conservation concerns) and lower than targets when recruitment was high (resulting in foregone catch). Scientists and managers can at least partially account for effects of such deviations between realized and target mortality rates (outcome uncertainties) by choosing target harvest rules that reflect typical patterns in those deviations. We derived a method to permit modelers to incorporate those patterns into analyses of management options. [ABSTRACT FROM AUTHOR]

Sibling – age-class (sibling) models, which relate abundance of one age-class of adult sockeye salmon (Oncorhynchus nerka) to abundance of the previous age-class in the previous year, are commonly used to forecast abundance 1 year ahead. Standard sibling models assume constant parameters over time. However, many sockeye salmon populations have shown temporal changes in age-at-maturity. We therefore developed a new Kalman filter sibling model that allowed for time-varying parameters. We found considerable evidence for long-term trends in parameters of sibling models for 24 sockeye salmon stocks in British Columbia and Alaska; most trends reflected increasing age-at-maturity. In a retrospective analysis, the Kalman filter forecasting models reduced mean-squared forecasting errors compared with standard sibling models in 29%–39% of the stocks depending on the age-class. The Kalman filter models also had mean percent biases closer to zero than the standard models for 54%–94% of the stocks. Parameters of these sibling models are positively correlated among stocks from different regions, suggesting that large-scale factors (e.g., competition among stocks for limited marine prey) may be important drivers of long-term changes in age-at-maturity schedules in sockeye salmon. [ABSTRACT FROM AUTHOR]

Environmental impacts on fisheries are pervasive, yet methods to account for them in stock assessments and management decisions vary in rigour and quality. The prevalence and efficacy of methods to account for environmental impacts are not well documented, limiting our ability to adequately respond to future environmental and climate changes for adaptive resource management. In Canada, legislation now requires that environmental conditions are considered in the management of fish stocks, yet the current extent of implementation in assessment processes is poorly understood. We assessed the use of climate, oceanographic and ecological considerations in science advisory processes for 178 stock assessments by Fisheries and Oceans Canada. We evaluated whether these considerations were included in conceptual hypotheses about broad‐scale mechanisms, quantitative or qualitative analyses, and the development of management advice on current or future stock status. Conceptual hypotheses were included in 46% of assessments; quantitative inclusions occurred in 21% of assessments, while qualitative interpretations appeared in 31% of assessments; and 27% of assessments included climate, oceanographic and/or ecological considerations in the advice. Assessments of salmonids, invertebrates and pelagic taxa more frequently made use of environmental data than those for groundfish and elasmobranchs. Comparing our findings with assessments in other jurisdictions highlighted a gap in Canada's ability to respond to environmental changes and a need to develop integrated management approaches, such as regional ecosystem assessments and approaches that combine modelling and empirical analyses, with socio‐economic analysis within interdisciplinary teams. [ABSTRACT FROM AUTHOR]

Information on biological status is essential for designing, implementing, and evaluating management strategies and recovery plans for threatened or exploited species. However, the data required to quantify status are often limited, and it is important to understand how assessments of status may be biased by assumptions in data analysis. For Pacific salmon, biological status assessments based on spawner abundances and spawner–recruitment (SR) analyses often involve "run reconstructions" that impute missing spawner data, expand observed spawner abundance to account for unmonitored streams, assign catch to individual stocks, and quantify age-at-return. Using a stochastic simulation approach, we quantified how common assumptions in run reconstructions biased assessments of biological status based on spawner abundance. We found that status assessments were robust to most common assumptions in run reconstructions, even in the face of declining monitoring coverage, but that overestimating catch tended to increase rates of status misclassification. Our results lend confidence to biological status assessments based on spawner abundances and SR analyses, even in the face of incomplete data. [ABSTRACT FROM AUTHOR]

Landscape models are increasingly used to classify and predict the structure and productivity of data‐limited aquatic ecosystems. One such suite of ecosystems is on the remote North and Central Coast (NCC) of British Columbia, where sockeye salmon (Oncorhynchus nerka) rear in more than 150 lakes. Given their remoteness and limited resources for assessment, limnological and population monitoring in many of these lakes has been periodic or absent, limiting understanding of the status of populations and their habitats. Lake photosynthetic rate (PR) estimates are foundational to models of sockeye salmon nursery lake productive capacity. Using data from 61 lakes across the NCC, we compared a suite of landscape and lake variables in an information theoretic framework producing a set of models relating these characteristics to lake PR. A categorical variable related to lake biogeochemistry—whether a lake is humic stained, clear, or glacially turbid—was the most important variable predicting lake PR and was included in all models. Lake surface area relative to upstream catchment size and lake perimeter‐to‐surface‐area ratio were also important, with smaller upstream catchments yielding higher production, and high shoreline complexity correlated with lower productivity as measured by limnetic PR. Model‐averaged predictions of PR from the four models with the lowest residual error were created for 96 lakes currently lacking limnological assessments. These landscape models represent a valuable starting point for evaluating lake‐specific carrying capacities for data‐poor sockeye salmon populations under Canada's Wild Salmon Policy. [ABSTRACT FROM AUTHOR]

Thirty-nine years of scale growth measurements from Big Qualicum River chum salmon ( Oncorhynchus keta) in southern British Columbia demonstrated that competition and climate variation affect marine growth and age-at-maturity. A longitudinal study design that accounted for correlation among individuals revealed growth at all ages was reduced when the biomass of North American chum, sockeye ( Oncorhynchus nerka), and pink salmon ( Oncorhynchus gorbuscha) was high. When North Pacific Gyre Oscillation (NPGO) was positive, indicating increased primary productivity, predicted growth increased. Climate variation influenced competition effects. For instance, density-dependent competition effects increased when NPGO became more positive and Pacific Decadal Oscillation became more negative (indicating cool conditions), causing the greatest range in predicted scale size. Chum salmon are likely to exhibit continued reduction in growth at age due to increased ocean temperatures driven by climate change and high aggregate salmon biomass that includes hatchery releases. If evidence of biomass and climate effects presented here are common among Pacific salmon populations, reduction of hatchery releases should be considered. [ABSTRACT FROM AUTHOR]

As the oceans absorb anthropogenic CO2 they become more acidic, a problem termed ocean acidification (OA). Since this increase in CO2 is occurring rapidly, OA may have profound implications for marine ecosystems. In the temperate northeast Pacific, fisheries play key economic and cultural roles and provide significant employment, especially in rural areas. In British Columbia (BC), sport (recreational) fishing generates more income than commercial fishing (including the expanding aquaculture industry). Salmon (fished recreationally and farmed) and Pacific Halibut are responsible for the majority of fishery-related income. This region naturally has relatively acidic (low pH) waters due to ocean circulation, and so may be particularly vulnerable to OA. We have analyzed available data to provide a current description of the marine ecosystem, focusing on vertical distributions of commercially harvested groups in BC in the context of local carbon and pH conditions. We then evaluated the potential impact of OA on this temperate marine system using currently available studies. Our results highlight significant knowledge gaps. Above trophic levels 2–3 (where most local fishery-income is generated), little is known about the direct impact of OA, and more importantly about the combined impact of multi-stressors, like temperature, that are also changing as our climate changes. There is evidence that OA may have indirect negative impacts on finfish through changes at lower trophic levels and in habitats. In particular, OA may lead to increased fish-killing algal blooms that can affect the lucrative salmon aquaculture industry. On the other hand, some species of locally farmed shellfish have been well-studied and exhibit significant negative direct impacts associated with OA, especially at the larval stage. We summarize the direct and indirect impacts of OA on all groups of marine organisms in this region and provide conclusions, ordered by immediacy and certainty. [ABSTRACT FROM AUTHOR]

Eleven Designatable Units (DUs) of Chinook Salmon (Oncorhynchus tshawytscha), within the Fraser River were assessed as Threatened or Endangered by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in 2018, and are currently under consideration for addition to Schedule 1 of the Species at Risk Act (SARA). The first part of the Recovery Potential Assessment (RPA) (Elements 1-11) provided DU descriptions, status updates and an assessment of the threats and factors limiting recovery. This second half provides potential recovery targets, a discussion of mitigation measures, population projections and a recommendation on allowable harm. Survival and recovery targets for each DU were suggested based on Wild Salmon Policy (WSP) benchmarks, with additional requirements about observed percent change in spawners. A projection model was used to assess likely future trajectories and the chances of meeting these targets, however, results are only available for DU2 (LFRHarrison). Despite efforts to produce the required input parameters for the stream-type DUs, significant uncertainties and a considerable lack of data prevented quantitative assessment, and hence these DUs were assessed qualitatively. Results for DU2 (LFR-Harrison) indicate that reaching the survival target under recent conditions is about as likely as not likely (48% chance), while meeting the recovery goal is unlikely (16% chance). Risks imposed by climate change and continued anthropogenic development add additional uncertainty that was only described qualitatively. Based on the quantitative assessment for DU2 (LFR-Harrison) and the qualitative assessment for the remaining DUs, it is recommended that human-induced mortality and other sources of harm identified in the threats assessment should be significantly reduced and in some cases prevented to provide the best chance for these populations to recover. [ABSTRACT FROM AUTHOR]

Canada's Fisheries Act was revised on June 21, 2019, resulting in new Considerations and Fish Stocks provisions (FSP) that relate to the management of fisheries. The FSP (Section 6) contains new terminology: 1) a requirement to implement measures to maintain major fish stocks "at or above the level necessary to promote the sustainability of the stock" (s 6.1(1)); and 2) if those management measures are unfeasible due to cultural or socio-economic impacts, to maintain stocks above the limit reference point or LRP (s 6.1(2)), which is a biological threshold to serious harm. Definitions of sustainability recognize both time and the need for equitable access to benefits across generations of resource users. Most jurisdictions recognize multiple axes of sustainability including ecological, socio-economic and institutional axes, but prioritize them differently. Consideration of all axes is necessary to operationalize fisheries management to support sustainable use, and science alone cannot advise on all of them. A pragmatic definition of sustainability in fisheries is that it is the process that conveys the ability to maintain a specified level of practical and effective use of a fisheries resource over the long term, where practical and effective reflects value-based measureable objectives related to biological, socio-economic and cultural outcomes. In the same vein, a level necessary to promote sustainability of the stock can be defined as "a threshold representing a specified level of practical and effective resource use over the long term." In the absence of clearly-defined value-based objectives for resource use or tolerance for risk to the stock, the threshold cannot be defined more specifically. Thresholds and other levels fulfilling s 6.1(1) or s 6.1(2) differ with respect to trade-offs among biological, socio-economic, and/or cultural objectives but both sections imply the stock be maintained above the LRP. Limits, other thresholds and target reference points play important roles in constraining which stock states are considered sustainable internationally. Review of Canada's PA Policy suggests that fisheries sustainability could be evaluated, in part, by considering whether stock status exceeds the LRP and whether fishing mortality is less than the removal reference rate. The question of sustainability can also be assessed by evaluating whether management measures are expected to perform acceptably with respect to stated limits and targets over specified time frames. The multiple axes of sustainability imply there is a role for multiple sectors in defining and promoting stock and fisheries sustainability. The Science Sector sets LRPs, evaluates stock status against reference points, and may contribute by evaluating other elements of the ecological axis of sustainability such as age or size composition of the stock, habitat, trophic level and other ecosystem considerations in relation to objectives. Setting targets, other thresholds, time frames and determining acceptable risks are value-based choices and cannot be established via scientific means alone. All Sectors may benefit from Departmental guidance as to how s 6.1(1) and s 6.1(2) differ in implementation, particularly with respect to the use of PA Policy reference points in management objectives, and implications for management measures including harvest control rules. [ABSTRACT FROM AUTHOR]

Identifying factors that influence anadromous Pacific salmon (Oncorhynchus spp.) population dynamics is complicated by their diverse life histories and large geographic range. Over the last several decades, Chinook salmon (O. tshawytscha) populations from coastal areas and the Salish Sea have exhibited substantial variability in abundance. In some cases, populations within the Salish Sea have experienced persistent declines that have not rebounded. We analyzed a time series of early marine survival from 36 hatchery Chinook salmon populations spanning ocean entry years 1980-2008 to quantify spatial and temporal coherence in survival. Overall, we observed higher inter-population variability in survival for Salish Sea populations than non-Salish Sea populations. Annual survival patterns of Salish Sea populations covaried over smaller spatial scales and exhibited less synchrony among proximate populations relative to non-Salish Sea populations. These results were supported by multivariate autoregressive state space (MARSS) models which predominantly identified region-scale differences in survival trends between northern coastal, southern coastal, Strait of Georgia, and Puget Sound population groupings. Furthermore, Dynamic Factor Analysis (DFA) of regional survival trends showed that survival of southern coastal populations was associated with the North Pacific Gyre Oscillation, a large-scale ocean circulation pattern, whereas survival of Salish Sea populations was not. In summary, this study demonstrates that survival patterns in Chinook salmon are likely determined by a complex hierarchy of processes operating across a broad range in spatial and temporal scales, presenting challenges to the management of mixed-stock fisheries. [ABSTRACT FROM AUTHOR]

Quantifying the variability in the delivery of ecosystem services across the landscape can be used to set appropriate management targets, evaluate resilience and target conservation efforts. Ecosystem functions and services may exhibit portfolio-type dynamics, whereby diversity within lower levels promotes stability at more aggregated levels. Portfolio theory provides a framework to characterize the relative performance among ecosystems and the processes that drive differences in performance., We assessed Pacific salmon Oncorhynchus spp. portfolio performance across their native latitudinal range focusing on the reliability of salmon returns as a metric with which to assess the function of salmon ecosystems and their services to humans., We used the Sharpe ratio (e.g. the size of the total salmon return to the portfolio relative to its variability (risk)) to evaluate the performance of Chinook and sockeye salmon portfolios across the west coast of North America. We evaluated the effects on portfolio performance from the variance of and covariance among salmon returns within each portfolio, and the association between portfolio performance and watershed attributes., We found a positive latitudinal trend in the risk-adjusted performance of Chinook and sockeye salmon portfolios that also correlated negatively with anthropogenic impact on watersheds (e.g. dams and land-use change). High-latitude Chinook salmon portfolios were on average 2·5 times more reliable, and their portfolio risk was mainly due to low variance in the individual assets. Sockeye salmon portfolios were also more reliable at higher latitudes, but sources of risk varied among the highest performing portfolios., Synthesis and applications. Portfolio theory provides a straightforward method for characterizing the resilience of salmon ecosystems and their services. Natural variability in portfolio performance among undeveloped watersheds provides a benchmark for restoration efforts. Locally and regionally, assessing the sources of portfolio risk can guide actions to maintain existing resilience (protect habitat and disturbance regimes that maintain response diversity; employ harvest strategies sensitive to different portfolio components) or improve restoration activities. Improving our understanding of portfolio reliability may allow for management of natural resources that is robust to ongoing environmental change. [ABSTRACT FROM AUTHOR]

Population diversity can stabilize ecological dynamics and increase resilience to future environmental change. In exploited systems, however, management goals to preserve diversity may be in tension with harvest objectives. For example, fisheries managers may forgo opportunities to sustainably harvest abundant populations to reduce risks to less productive populations. Increasing the stock selectivity of fisheries is one management lever that may allow for both conservation- and catch-based objectives to be met. We developed a model that simulates the dynamics of a Pacific salmon stock aggregate and its fishery to evaluate how changing allocations between mixed- and single-stock fisheries influences management performance. We focused on relatively generic management strategies that may be implemented in a range of salmon fisheries. Additionally, we examined how the relative performance of mixed- and single-stock fisheries may change under alternative ecological and management scenarios. We found that increasing single-stock fishery allocations increased aggregate abundance and improved the status of some stocks relative to their conservation benchmarks. However, these improvements did not occur uniformly–relatively abundant, productive stocks exhibited no change, or even declines, in conservation performance as single-stock fishery allocations increased. Furthermore, differences in performance between mixed- and single-stock fisheries were reduced when productivity was uniformly low, when the mixed-stock fishery was managed conservatively, or when mortality during freshwater migrations was high. While single-stock fisheries can increase the probability that conservation-based objectives will be met, they are not a panacea and may only be effective when specific conditions are met. [ABSTRACT FROM AUTHOR]

Discusses contemporary visions of progress in ecological studies. Changes that ecology has witnessed; View that modern ecology is observational, experimental, and theoretical analyses of patterns and process; Support for the explicit clarification of terminology in ecological studies; Creation of easily accessible and up-to-date compendium of ecological terms.