Canadian Journal of Fisheries and Aquatic Sciences, Ahead of Print.
Migrating adult Pacific salmon (Oncorhynchus spp.) are sensitive to warm water (>18 °C), with a range of consequences from decreased spawning success to early mortality. We examined the proportion of Yukon River Chinook salmon (O. tshawytscha) exhibiting evidence of heat stress to assess the potential that high temperatures contribute to freshwater adult mortality in a northern Pacific salmon population. Water temperatures greater than 18 °C have occurred almost annually in the Yukon River and correspond with low population abundance since the 1990s. Using gene transcription products and heat shock protein 70 biomarkers validated by field experiment, we identified heat stress in half of Chinook salmon examined (54%, n = 477) across three mainstem locations and three tributaries in 2016–2017. Biomarkers tracked wide variation in water temperature (14–23 °C) within a tributary. The proportion of salmon with heat stress differed between years at four of the six locations, with more prevalent heat stress in the warmer year. This work demonstrates that warming water temperatures are currently affecting northern populations of Pacific salmon.

中文翻译：

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育空河奇努克鲑鱼普遍热应激的证据

《加拿大渔业和水生科学杂志》，印刷前。
迁徙的成年太平洋鲑鱼（Oncorhynchus spp。）对温水（> 18°C）敏感，其后果包括产卵成功率下降和早期死亡。我们检查了育空河奇努克鲑（O. tshawytscha）表现出热应激的比例，以评估高温可能导致北太平洋鲑鱼种群中淡水成年死亡。自1990年代以来，育空河几乎每年都发生高于18°C的水温，这与人口稀少相对应。我们使用基因转录产物和热休克蛋白70种生物标记物（已通过现场实验验证），在2016–2017年间在三个主干位置和三个支流中的一半奇努克鲑鱼（54％，n = 477）中鉴定出热应激。生物标志物追踪支流中水温（14–23°C）的广泛变化。在六个地点中有四个地点，受热应激的鲑鱼比例在不同年份之间有所不同，在较暖的一年中，热应激更为普遍。这项工作表明，水温升高目前正在影响太平洋鲑鱼的北部种群。