We developed spatially explicit representations for seasonal high-seas (open ocean) thermal habitats for six species of Pacific salmon (Oncorhynchus spp.) and evaluated the effects of natural climate variability and projected changes under three Intergovernmental Panel on Climate Change scenarios of future greenhouse gas emissions. Changes in high-seas habitat due to natural climatic variation in 20th century were small relative to that under anthropogenic climate change scenarios for the middle to late 21st century. Under a multimodel ensemble average of global climate model outputs using A1B (medium) emissions scenario for the entire study area (North Pacific and part of Arctic Ocean), projected winter habitats of sockeye (Oncorhynchus nerka) decreased by 38%, and summer habitat decreased by 86% for Chinook (Oncorhynchus tshawytscha), 45% for sockeye, 36% for steelhead (Oncorhynchus mykiss), 30% for coho (Oncorhynchus kisutch), 30% for pink (Oncorhynchus gorbuscha), and 29% for chum (Oncorhynchus keta) salmon by 2100. Reductions were 25% lower for B1 (lower) emissions and 7% higher for A2 (higher) emissions scenarios. Projected habitat losses were largest in the Gulf of Alaska and western and central subarctic North Pacific. Nearly complete losses of Gulf of Alaska habitat for sockeye in both seasons and Chinook in summer raise important policy issues for North American fishery managers and governments.Résumé : Nous mettons au point des représentations spatialement explicites des habitats thermiques saisonniers de hautemer (au large) de six espèces de saumons du Pacifique (Oncorhynchus spp.) et évaluons les effets de la variabilité climatique naturelle et des changements prévus dans trois scénarios d'émissions futures de gaz à effets de serre produits par le Panel intergouvernemental sur le changement climatique. Les changements dans l'habitat de haute-mer dus à la variation climatique naturelle au 20 ième siècle sont faibles par comparaison aux scénarios de changements climatiques anthropiques prédits pour le milieu et la fin du 21 e siècle. Dans la moyenne d'un ensemble multi-modèles de projections faites par des modèles de climat global, utilisant le scénario A1B (moyen) pour les émissions dans l'ensemble de la région (Pacifique Nord et partie de l'Océan Arctique), les habitats d'hiver prédits pour le saumon rouge (Oncorhynchus nerka) diminuent de 38 % et les habitats d'été sont réduits de 86 % pour le saumon chinook (Oncorhynchus tshawytscha), 45 % pour le saumon rouge, 36 % pour la truite arc-en-ciel anadrome (Oncorhynchus mykiss), 30 % pour le saumon coho (Oncorhynchus kisutch), 30 % pour le saumon rose (Oncorhynchus gorbuscha) et 29 % pour le saumon kéta (Oncorhynchus keta) vers l'année 2100. Les réduc-tions sont 25 % plus basses avec le scénario B1 (plus faible) d'émissions et 7 % plus fortes pour le scénario (plus élevé) A2. Les pertes prédites d'habitat sont les plus importantes dans le golfe de l'Alaska et les portions ouest et centrales du Pacifique Nord arctique. Les pertes presque complètes de l'h...
We genotyped Chinook salmon (Oncorhynchus tshawytscha) from the Bering Sea and North Pacific Ocean for 43 singlenucleotide polymorphisms (SNPs) to investigate seasonal distribution and migration patterns. We analyzed 3563 immature fish from 22 spatiotemporal strata; composition analyses were performed using genotype data from spawning stocks spanning the species range. Substantial variation in stock composition existed among spatial and seasonal strata. We inferred patterns of seasonal migration based upon these data along with data from previous tag, scale, and parasite studies. We found that stocks from western Alaska and Yukon River overwinter on the Alaska continental shelf then travel to the middle and western Bering Sea during spring-fall. Stocks from California to Southeast Alaska were distributed in Gulf of Alaska year-round, with a substantial portion of this group migrating northward to the eastern Bering Sea during spring-fall. Proportions of Russian stocks increase when moving east to west in both the Bering Sea and North Pacific Ocean. These data can be used to better understand the impacts of fisheries and climate change on this valuable resource.
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