Solokas Mary A, Feiner Zachary S, Al-Chokachy Robert, Budy Phaedra, DeWeber J Tyrell, Sarvala Jouko, Sass Greg G, Tolentino Scott A, Walsworth Timothy E, Jensen Olaf P
Center for Limnology, University of Wisconsin, Madison, Wisconsin, USA.
Office of Applied Science, Wisconsin Department of Natural Resources, Madison, Wisconsin, USA.
Glob Chang Biol. 2023 May;29(9):2478-2492. doi: 10.1111/gcb.16626. Epub 2023 Feb 28.
Declining body size is believed to be a universal response to climate warming and has been documented in numerous studies of marine and anadromous fishes. The Salmonidae are a family of coldwater fishes considered to be among the most sensitive species to climate warming; however, whether the shrinking body size response holds true for freshwater salmonids has yet to be examined at a broad spatial scale. We compiled observations of individual fish lengths from long-term surveys across the Northern Hemisphere for 12 species of freshwater salmonids and used linear mixed models to test for spatial and temporal trends in body size (fish length) spanning recent decades. Contrary to expectations, we found a significant increase in length overall but with high variability in trends among populations and species. More than two-thirds of the populations we examined increased in length over time. Secondary regressions revealed larger-bodied populations are experiencing greater increases in length than smaller-bodied populations. Mean water temperature was weakly predictive of changes in body length but overall minimal influences of environmental variables suggest that it is difficult to predict an organism's response to changing temperatures by solely looking at climatic factors. Our results suggest that declining body size is not universal, and the response of fishes to climate change may be largely influenced by local factors. It is important to know that we cannot assume the effects of climate change are predictable and negative at a large spatial scale.
体型变小被认为是对气候变暖的一种普遍反应，并且在众多关于海洋鱼类和溯河产卵鱼类的研究中都有记载。鲑科是一类冷水鱼，被认为是对气候变暖最为敏感的物种之一；然而，在广阔的空间尺度上，淡水鲑科鱼类体型变小的反应是否成立尚待研究。我们汇总了北半球长期调查中12种淡水鲑科鱼类个体长度的观测数据，并使用线性混合模型来检验近几十年来体型（鱼的长度）的空间和时间趋势。与预期相反，我们发现总体长度显著增加，但不同种群和物种的趋势差异很大。我们研究的种群中超过三分之二的种群长度随时间增加。二次回归显示，体型较大的种群长度增加幅度大于体型较小的种群。平均水温对体长变化的预测作用较弱，但环境变量的总体影响极小，这表明仅通过观察气候因素很难预测生物体对温度变化的反应。我们的结果表明，体型变小并非普遍现象，鱼类对气候变化的反应可能在很大程度上受当地因素影响。重要的是要知道，我们不能假定气候变化的影响在大空间尺度上是可预测的且是负面的。
