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Pathways linking climate to population dynamics of higher-trophic-level fish species such as Pacific salmon often involve a hierarchy in which regional-scale physical and biological processes mediate the effects of large-scale climate variability. We used probabilistic networks to investigate 17 potential ecological pathways linking climate to Oregon coho salmon (Oncorhynchus kisutch) recruitment. We found that pathways originating with the Pacific Decadal Oscillation were the most influential on recruitment, with the net effect being two to four times greater than for pathways originating with the North Pacific Gyre Oscillation or the Oceanic Nino Index. Among all environmental variables, sea surface temperature and an index of juvenile salmon prey biomass had the greatest effects on recruitment, with a 76% chance of recruitment being equal to or below average given that ocean temperatures were above average and a 34% chance of recruitment being below average given that prey biomass was above average. Our results provide evidence that shifts in climate patterns could strongly influence recruitment simultaneously through multiple ecological pathways and highlight the importance of quantifying cumulative effects of these pathways on higher-trophic-level species. Les voies qui relient le climat a la dynamique des populations d'especes de poissons de niveau trophique eleve comme les saumons du Pacifique definissent une hierarchie dans laquelle des processus physiques et biologiques a l'echelle regionale modulent les effets de la variabilite a grande echelle du climat. Nous avons utilise des reseaux probabilistes pour etudier 17 voies ecologiques potentielles reliant le climat au recrutement du saumon coho (Oncorhynchus kisutch) de l'Oregon. Nous avons constate que les voies emanant de l'oscillation decennale du Pacifique exercent la plus grande influence sur le recrutement, leur effet net etant de deux a quatre fois superieur a celui des voies qui emanent de l'oscillation du tourbillon nord-pacifique ou de l'indice Nino oceanique. De toutes les variables environnementales, la temperature de la surface de la mer et un indice de biomasse des proies des saumons juveniles avaient les plus grands effets sur le recrutement, avec une probabilite de 76 % que le recrutement soit egal ou inferieur a la moyenne etant donne que les temperatures de l'ocean etaient superieures a la moyenne et une probabilite de 34 % que le recrutement soit inferieur a la moyenne etant donne que la biomasse de proies etait superieure a la moyenne. Nos resultats fournissent des preuves appuyant la these voulant que des changements des regimes climatiques puissent exercer simultanement une forte influence sur le recrutement par l'entremise de multiples voies ecologiques et ils soulignent l'importance de quantifier les effets cumulatifs de ces voies sur les especes de niveau trophique eleve. [Traduit par la Redaction], Introduction Pacific salmon (Oncorhynchus spp.) populations along the Northeast Pacific coast exhibit large interannual and interdecadal fluctuations in adult abundances. Changes in large-scale climate patterns are often associated with variability [...]

Better fisheries management is often given as one justification for research on improving forecasts of fish survival. However, the value gained from expected improvements in forecast skill in terms of achieving management goals is rarely quantified as part of research objectives. Using Monte Carlo simulations of population dynamics, we assessed the effect of forecast skill under two strategies for managing Oregon coast natural (OCN) coho salmon (Oncorhynchus kisutch). The first, or status quo, strategy is currently being used to rebuild threatened OCN coho populations. This strategy determines harvest based on both a forecasted marine survival rate and parental spawner abundance. The second strategy relies on a forecast of preharvest adult abundance to achieve a constant spawner escapement target. Performance of the status quo strategy was largely insensitive to forecast skill, while the second strategy showed sensitivity that varied with escapement target and specific performance metric. The results imply that effort towards improving forecasts is not justifiable solely on the basis of improved management under the status quo strategy, though it may be were the management strategy altered. Une meilleure gestion des ressources halieutiques est une des raisons communement evoquees pour justifier les recherches sur l'amelioration de la capacite de prevision de la survie du poisson. Cela dit, la quantification de la valeur decoulant des ameliorations attendues de la capacite de prevision pour ce qui est de l'atteinte des objectifs de gestion est rarement incluse dans les objectifs de recherche. En utilisant des simulations de Monte Carlo de la dynamique des populations, nous avons evalue l'effet de la capacite de prevision dans le contexte de deux strategies de gestion du saumon coho (Oncorhynchus kisutch) naturel de la cote de l'Oregon (OCN). La premiere strategie, celle du statu quo, est actuellement utilisee pour reconstituer les populations menacees de saumon coho OCN. Selon cette strategie, la recolte est etablie en fonction des previsions concernant le taux de survie en mer et l'abondance de geniteurs parentaux. La deuxieme strategie repose sur la prevision de l'abondance des adultes avant la recolte pour en arriver a une cible d'echappee de geniteurs constante. Le rendement de la strategie du statu quo s'est avere peu sensible a la capacite de prevision, alors que la sensibilite de la deuxieme strategie variait selon la cible d'echappee et le parametre de mesure du rendement utilise. Ces resultats indiquent que l'amelioration de la gestion dans le contexte d'une approche axee sur le statu quo ne justifie pas, a elle seule, les efforts visant l'amelioration des previsions, mais que ces efforts pourraient etre justifies si la strategie de gestion etait modifiee. [Traduit par la Redaction], Introduction Since the late 1800s, Pacific salmon have been a major component of the commercial fishery along the western coast of North America from California to Alaska (Magnuson et al. [...]

Generalized additive models (GAMs) were used to investigate the relationships between annual recruitment of natural coho salmon ( Oncorhynchus kisutch) from Oregon coastal rivers and indices of the physical ocean environment. Nine indices were examined, ranging from large-scale ocean indicators, e.g., Pacific Decadal Oscillation (PDO), to indicators of the local ecosystem (e.g., coastal water temperature near Charleston, OR). Generalized additive models with two and three predictor variables were evaluated using a set of performance metrics aimed at quantifying model skill in short-term (approximately 1 yr) forecasting. High explanatory power and promising forecast skill resulted when the spring/summer PDO averaged over the 4 yr prior to the return year was used to explain a low-frequency (multi-year) pattern in recruitment and one or two additional variables accounted for year-to-year deviations from the low-frequency pattern. More variance was explained when averaging the predictions from a set of models (i.e., taking the ensemble mean) than by any single model. Making multiple forecasts from a set of models also provided a range of possible outcomes that reflected, to some degree, the uncertainty in our understanding of how salmon productivity is driven by physical ocean conditions. [ABSTRACT FROM AUTHOR]