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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. Il est necessaire de disposer d'information sur l'etat biologique pour la conception, la mise en reuvre et Revaluation de strategies de gestion et de plans de retablissement visant des especes menacees ou exploitees. Les donnees requises pour quantifier cet etat sont toutefois souvent limitees, et il importe de comprendre comment des evaluations de l'etat peuvent etre biaisees par les hypotheses qui sous-tendent l'analyse des donnees. Pour les saumons du Pacifique, les evaluations de l'etat biologique reposant sur l'abondance de geniteurs et les analyses de recrutement-geniteurs (RG) comprennent souvent des << reconstitutions de montaison >> qui imputent des donnees manquantes sur les geniteurs, rehaussent l'abondance de geniteurs observee pour tenir compte des cours d'eau qui ne font pas l'objet d'une surveillance, assignent les prises a differents stocks et quantifient l'age au moment du retour. En utilisant une approche de simulation stochastique, nous quantifions comment des hypotheses repandues dans les reconstitutions de montaison biaisent les evaluations de l'etat biologique reposant sur l'abondance de geniteurs. Nous constatons que les evaluations de l'etat sont robustes pour la plupart des hypotheses courantes qui sous-tendent les reconstitutions de montaison, meme dans les cas ou la couverture de la surveillance diminue, mais que la surestimation des prises tend a accroitre la frequence de classifications erronees de l'etat. Nos resultats temoignent de la fiabilite des evaluations de l'etat biologique basees sur l'abondance de geniteurs et les analyses RG, meme dans des situations de donnees incompletes. [Traduit par la Redaction], Introduction Timely and effective management of fish and wildlife relies on accurate information about the current biological status of populations. Status assessments form the basis of many conservation decision-support tools, [...]

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 [AIC.sub.c] 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, [S.sub.MSY], 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. Les modeles integrant des parametres variables dans le temps sont de plus en plus utilises dans Revaluation des stocks de poissons, mais leur fiabilite en ce qui concerne la determination de points ou d'indices de reference biologiques n'a pas fait l'objet d'une evaluation exhaustive. Nous evaluons des modeles de recrutement au stock avec et sans productivite variable dans le temps dans un cadre de simulation pour le saumon sockeye (Oncorhynchus nerka) pour differents scenarios de productivite et d'exploitation. La non-prise en compte des tendances de la productivite mene a des surestimations de cette derniere et des sous-estimations de la capacite quand les taux d'exploitation et la productivite baissent au fil du temps, ce qui se traduit par une sous-estimation en moyenne des indices de l'etat biologique. Meme s'ils sont moins biaises, les modeles variables dans le temps donnent un ajustement assez pauvre pour les criteres de selection de modeles de types CIA et CIB. Les resultats de nos simulations sont compares a des analyses empiriques de 12 stocks de saumons sockeyes de fleuve Fraser en Colombie-Britannique (Canada). Si les indices bases sur des modeles variables dans le temps sont moins biaises, les vrais indices sous-jacents bases sur l'abondance de geniteurs au rendement equilibre maximum, SREM, suivent des tendances descendantes quand la productivite baisse, ce qui pourrait ne pas correspondre aux objectifs de conservation. Nous concluons en abordant les meilleures pratiques a employer pour adapter des indices biologiques a la productivite variable dans le temps. [Traduit par la Redaction], Introduction Accounting for environmental variability and its effects on stock productivity is increasingly being recognized as a priority for fisheries management (King et al. 2015). Success incorporating environmental drivers into [...]

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. Des mesures sur 39 ans de la croissance des ecailles de saumons ketas (Oncorhynchus keta) de la Grande riviere Qualicum, dans le sud de la Colombie-Britannique, demontrent que la concurrence et les variations climatiques ont une incidence sur la croissance en mer et l'age a la maturite. Un plan d'etude longitudinale qui tient compte de la correlation entre individus revele que la croissance a tous les ages est plus faible quand la biomasse des saumons ketas, sockeyes (Oncorhynchus nerka) et roses (Oncorhynchus gorbuscha) d'Amerique du Nord est elevee. Quand l'oscillation du tourbillon nord-pacifique (OTPN) est positive, indiquant une productivite primaire accrue, la croissance predite augmente. Les variations du climat ont egalement une incidence sur ces effets de concurrence. Les effets de la concurrence dependant de la densite augmentent quand l'OTPN devient plus positive et l'oscillation decennale du Pacifique, plus negative (indiquant des conditions fraiches), ce qui produit la plus grande fourchette de tailles d'ecailles predites. Il est probable que les saumons ketas continueront de presenter une diminution de la croissance selon l'age en raison de la hausse des temperatures oceaniques causee par les changements climatiques et de la forte biomasse totale de saumons incluant les individus issus d'ecloseries. Si les indices d'effets de la biomasse et du climat releves dans la presente etude s'averaient repandus dans les populations de saumons du Pacifique, il serait pertinent d'examiner la possibilite de reduire les lachers de poissons issus d'ecloseries., Introduction There have been recent downward trends in size-at-age for many Pacific salmon (Oncorhynchus spp.) populations (Pyper and Peterman 1999; Agler et al. 2013; Jeffrey et al. 2017), which are [...]

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]

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 (Oncorhynchus 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 (Oncorhynchus kisutch). 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. La repartition des individus entre les populations et dans l'espace peut contribuer a leur resilience en presence de variabilite environnementale. Des changements dans la repartition peuvent indiquer la perte de sous-populations genetiquement distinctes, la deterioration de la capacite de l'habitat, ou les deux. Les agences de gestion americaines et canadiennes ont recemment reconnu la repartition des saumons du Pacifique (Oncorhynchus spp.) entre les sites de fraie comme une composante importante de la determination de leur statut; les metriques de la repartition de la fraie n'ont cependant pas ete evaluees de maniere rigoureuse. Nous evaluons trois metriques de la repartition de la fraie et trois plans d'echantillonnage en ce qui a trait a leur capacite a deceler des contractions simulees dans la production de saumons coho (Oncorhynchus kisutch). Nous avons simule la dynamique de la population a 100 sites a l'aide d'un modele reproducteurs-recrues qui tient compte de la variabilite naturelle du recrutement, de l'age a la maturite, de la dispersion et de l'erreur de mesure dans les observations d'abondances. Des analyses de sensibilite indiquent que de grandes erreurs d'observation et l'errance des reproducteurs loin de leurs cours d' eau de naissance peuvent masquer les changements dans la repartition. De plus, la surveillance des seuls sites a forte densite de reproducteurs, comme on le fait souvent, n'arrive pas a reconnaitre la contraction simulee de la production, ce qui souligne l'importance d'adapter les programmes de surveillance aux objectifs de l'evaluation. [Traduit par la Redaction], Introduction Endangered or exploited species are commonly assigned to units of conservation (Green 2005) that reflect irreplaceable geographic and genetic diversity within that species. The distribution of individuals within these [...]

Abstract: 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 [...]

Abstract: 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, [...]

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]