Institute of Marine Sciences, University of California Santa Cruz, Santa Cruz, CA, USA.
Fisheries Ecology Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Santa Cruz, CA, USA.
Glob Chang Biol. 2021 Feb;27(3):536-549. doi: 10.1111/gcb.15450. Epub 2020 Dec 4.
Migratory species are particularly vulnerable to climate change because habitat throughout their entire migration cycle must be suitable for the species to persist. For migratory species in rivers, predicting climate change impacts is especially difficult because there is a lack of spatially continuous and seasonally varying stream temperature data, habitat conditions can vary for an individual throughout its life cycle, and vulnerability can vary by life stage and season. To predict thermal impacts on migratory riverine populations, we first expanded a spatial stream network model to predict mean monthly temperature for 465,775 river km in the western U.S., and then applied simple yet plausible future stream temperature change scenarios. We then joined stream temperature predictions to 44,396 spatial observations and life-stage-specific phenology (timing) for 26 ecotypes (i.e., geographically distinct population groups expressing one of the four distinct seasonal migration patterns) of Chinook salmon (Oncorhynchus tshawytscha), a phenotypically diverse anadromous salmonid that is ecologically and economically important but declining throughout its range. Thermal stress, assessed for each life stage and ecotype based on federal criteria, was influenced by migration timing rather than latitude, elevation, or migration distance such that sympatric ecotypes often showed differential thermal exposure. Early-migration phenotypes were especially vulnerable due to prolonged residency in inland streams during the summer. We evaluated the thermal suitability of 31,699 stream km which are currently blocked by dams to explore reintroduction above dams as an option to mitigate the negative effects of our warmer stream temperature scenarios. Our results showed that negative impacts of stream temperature warming can be offset for almost all ecotypes if formerly occupied habitat above dams is made available. Our approach of combining spatial distribution and phenology data with spatially explicit and temporally explicit temperature predictions enables researchers to examine thermal exposure of migrating populations that use seasonally varying habitats.
迁徙物种特别容易受到气候变化的影响，因为它们在整个迁徙周期中所需的栖息地都必须适合物种生存。对于河流中的迁徙物种来说，预测气候变化的影响尤其困难，因为缺乏空间连续且季节变化的溪流温度数据，栖息地条件在个体的整个生命周期中可能会发生变化，并且脆弱性可能因生命阶段和季节而异。为了预测对迁徙河流种群的热影响，我们首先扩展了一个空间溪流网络模型，以预测美国西部 465,775 公里的河流的月平均温度，然后应用了简单但合理的未来溪流温度变化情景。然后，我们将溪流温度预测与 44,396 个空间观测值和 26 个生态型（即地理上不同的种群群体，表现出四种不同季节性迁徙模式之一）的特定生命阶段的物候（时间）相结合，这些生态型是表型多样的溯河洄游性鲑鱼（Oncorhynchus tshawytscha），这是一种生态和经济上重要但在其分布范围内下降的鲑鱼。根据联邦标准，基于每个生命阶段和生态型评估热应激，受到迁徙时间的影响而不是纬度、海拔或迁徙距离的影响，使得同域生态型通常表现出不同的热暴露。由于夏季在内陆溪流中停留时间较长，早期迁徙表型尤其脆弱。我们评估了目前被大坝阻断的 31,699 公里溪流的热适宜性，以探讨在大坝上重新引入作为缓解我们更暖溪流温度情景负面影响的一种选择。我们的研究结果表明，如果可以利用以前占据的大坝上方栖息地，则几乎可以抵消所有生态型的溪流温度变暖的负面影响。我们将空间分布和物候数据与空间明确和时间明确的温度预测相结合的方法使研究人员能够检查使用季节性变化生境的迁徙种群的热暴露情况。
