Spatio-temporal temperature variation influences juvenile steelhead (Oncorhynchus mykiss) use of thermal refuges
Spatio-temporal temperature variation influences juvenile steelhead (Oncorhynchus mykiss) use of thermal refuges
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DOI：
10.1890/es14-00036.1
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发表时间：
2014-07-01
期刊：
影响因子：
2.7
通讯作者：
Danner, Eric M.
中科院分区：
文献类型：
--
作者：
Brewitt, Kim S.;Danner, Eric M.
对于处于热耐受极限的物种来说，热避难所可能构成关键栖息地，特别是考虑到大规模的栖息地退化以及生态系统中气温的上升。克拉马斯河是一个高度改变的水系，夏季干流温度达到对受威胁的太平洋鲑鱼种群产生生理压力的水平，使得当温度接近热上限阈值时，热避难所对于夏季生存至关重要。水温的微小变化会对鲑鱼的生长和生存产生重大影响，因此精细的时空温度变化可能会影响避难所在何时何地对个体生存和种群持续存在具有重要意义。在这项研究中，我们将环境变量监测与鱼体温度测量（作为避难所使用的替代指标）相结合，以量化幼年虹鳟（Oncorhynchus mykiss）对热避难所的使用情况。我们使用逻辑混合效应模型来确定瞬时干流温度和流量、日以下温度变化、体型以及一天中的时间对虹鳟使用避难所的相对影响。干流温度是避难所使用的最强预测因子；当干流温度达到22 - 23℃时，大多数（>80%）幼年虹鳟会进入避难所，并且所有鱼在25℃时都会进入。随着干流日温度变化增加以及干流和支流之间的温差增大，鱼更有可能使用避难所。此外，虹鳟在避难所使用上表现出明显的昼夜行为变化，且这种变化因体型而异；较小的幼鱼（约160毫米）在夜间使用避难所的可能性比白天大得多，而较大的幼鱼（约210毫米）表现出的昼夜行为变化则不太明显。考虑到流域改变和气候变化的影响以及避难所栖息地日益增加的重要性，这些研究结果表明，物种的持续存在可能取决于极其精细的时空温度动态。
Thermal refuges form potentially critical habitat for species at the limits of their thermal tolerance, especially given large-scale habitat degradation and rising temperatures across ecosystems. The Klamath River is a highly altered system where summer mainstem temperatures reach levels that are physiologically stressful to threatened Pacific salmonid populations, making thermal refuges critical for over-summer survival when temperatures near upper thermal thresholds. Small changes in water temperature can have a large effect on salmonid growth and survival, and therefore fine-scale spatio-temporal temperature variation could influence when and where refuges are important for both individual survival and population persistence. In this study, we combined monitoring of environmental variables with measures of fish temperature (a proxy for refuge use) to quantify juvenile steelhead (Oncorhynchus mykiss) use of thermal refuges. We used a logistic mixed effects model to determine the relative influence of instantaneous mainstem temperature and flow, sub-daily temperature variation, body size, and time of day on steelhead refuge use. Mainstem temperature was the strongest predictor of refuge use; the majority (>80%) of juvenile steelhead moved into refuges when mainstem temperatures reached 22-23 degrees C, and all fish moved in by 25 degrees C. Fish were more likely to use refuges with increased diel mainstem temperature variation and larger temperature differential between the mainstem and tributary. In addition, steelhead exhibited a distinct diel behavioral shift in refuge use that varied with body size; smaller juveniles (similar to 160 mm) were much more likely to use refuges during the night than day, whereas larger juveniles (similar to 210 mm) exhibited a much less pronounced diel behavioral shift. Given impacts of watershed alteration and climate change and the growing importance of refuge habitat, these findings suggest that species persistence may depend on extremely fine-scale spatial and temporal temperature dynamics.