Abstract Pacific Lamprey (Entosphenus tridentatus) are a native anadromous species that, like salmon, historically returned to spawn in large numbers in watersheds along the west coast of the United States (U.S.). Lamprey play a vital role in river ecosystems and are one of the oldest vertebrates that have persisted over time likely influencing the evolution of many aquatic species. Pacific Lamprey have declined in abundance and are restricted in distribution throughout Washington, Oregon, Idaho and California. A key uncertainty influencing Pacific Lamprey status is the impact of climate change. We modified the NatureServe Climate Change Vulnerability Index (CCVI) to accommodate climate predictions from the International Panel on Climate Change. Using downscaled information, we characterized changes in 15 rivers occupied by Pacific Lamprey in the western U.S. We evaluated this risk under Representative Concentration Pathways (RCP) 4.5 and 8.5 for two time periods (mid-century 2040–2069 and end-century 2070–2099). The CCVI scores generally increased when going from RCP 4.5 to RCP 8.5 in three Global Climate Models for both mid-century and end-century, which our analyses forecasts degraded stream temperature and hydrologic conditions under increasing greenhouse gas emissions. The geographically assessed results suggest that climate change impacts to Pacific Lamprey vulnerability are magnified in highly altered rivers. If we continue to observe greenhouse gas emission levels associated with the RCP 8.5, Pacific Lamprey will be at greater risk to climate change impacts. In order to mitigate the risk from climate change toward the end of the century, additional actions will need to be prioritized to rapidly reduce the impact of these threats such as increasing flow, creating backwater habitat, restoring riparian vegetation and reducing stream disturbances. The findings revealed the patterns of vulnerability for Pacific Lamprey across their U.S. range are informative for prioritizing river restoration actions when paired with regional implementation plans.

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美国西部河流中太平洋七鳃鳗的气候变化脆弱性评估

摘要 太平洋七鳃鳗 (Entosphenus tridentatus) 是一种本土溯河物种，与鲑鱼一样，历史上曾在美国西海岸的流域大量产卵。七鳃鳗在河流生态系统中发挥着至关重要的作用，是最古老的脊椎动物之一，随着时间的推移一直存在，可能会影响许多水生物种的进化。太平洋七鳃鳗数量减少，分布在华盛顿州、俄勒冈州、爱达荷州和加利福尼亚州。影响太平洋七鳃鳗状况的一个关键不确定性是气候变化的影响。我们修改了 NatureServe 气候变化脆弱性指数 (CCVI) 以适应国际气候变化专门委员会的气候预测。使用缩小的信息，我们描述了美国西部太平洋七鳃鳗所占据的 15 条河流的变化 我们在代表性浓度路径 (RCP) 4.5 和 8.5 下评估了两个时间段（2040 年中叶至 2069 年和世纪末 2070 年至 2099 年）的风险。在本世纪中叶和本世纪末的三个全球气候模型中，当从 RCP 4.5 到 RCP 8.5 时，CCVI 得分普遍增加，我们的分析预测了在温室气体排放增加的情况下河流温度和水文条件下降。地理评估结果表明，气候变化对太平洋七鳃鳗脆弱性的影响在高度改变的河流中被放大。如果我们继续观察与 RCP 8.5 相关的温室气体排放水平，太平洋七鳃鳗将面临更大的气候变化影响风险。到本世纪末，为了减轻气候变化带来的风险，需要优先采取其他行动，以迅速减少这些威胁的影响，例如增加流量、创造回水栖息地、恢复河岸植被和减少河流干扰。调查结果揭示了太平洋七鳃鳗在其美国范围内的脆弱性模式，当与区域实施计划相结合时，可以为优先考虑河流恢复行动提供信息。