Forest Research Center, Instituto Superior de Agronomia, University of Lisbon, Portugal; Institute of Hydrobiology and Aquatic Ecosystem Management, University of Natural Resources and Life Sciences, Vienna, Austria.
Institute of Hydrobiology and Aquatic Ecosystem Management, University of Natural Resources and Life Sciences, Vienna, Austria.
J Environ Manage. 2021 Aug 15;292:112737. doi: 10.1016/j.jenvman.2021.112737. Epub 2021 May 12.
Rivers of the large Alpine valleys constitute iconic ecosystems that are highly threatened by multiple anthropogenic stressors. This stressor mix, however, makes it difficult to develop and refine conservation and restoration strategies. It is, therefore, urgent to acquire more detailed knowledge on the consequences and interactions of prevalent stressors on fish populations, in particular, on indicator species such as the European grayling Thymallus thymallus. Here, we conducted a multi-river, multi-stressor investigation to analyze the population status of grayling. Using explorative decision-tree approaches, we disentangled the main and interaction effects of four prevalent stressor groups: flow modification (i.e., hydropeaking), channelization, fragmentation, and water quality alteration. Moreover, using a modified variant of the bootstrapping method, pooled bootstrapping, we determined the optimal number of characteristics that adequately describe fish population status. In our dataset, hydropeaking had the strongest single effect on grayling populations. Grayling biomass at hydrological control sites was around eight times higher than at sites affected by hydropeaking. The primary parameters for predicting population status were downramping rate and peak amplitude, with critical ranges of 0.2-0.4 cm min and 10-25 cm. In hydropeaking rivers, river morphology and connectivity were the preceding subordinated parameters. Repeating the procedure with pooled bootstrapping datasets strengthened the hypothesis that the identified parameters are most relevant in predicting grayling population status. Hence, hydropeaking mitigation based on ecological thresholds is key to protect and restore already threatened grayling populations. In hydropeaking rivers, high river network connectivity and heterogenous habitat features can dampen the adverse effects of pulsed-flow releases by offering shelter and habitats for all life cycle stages of fish. The presented approach of explorative tree analysis followed by post-hoc tests of identified effects, as well as the pooled bootstrapping method, offers a simple framework for researchers and managers to analyze multi-factorial datasets and draw solid management conclusions.
阿尔卑斯山大型山谷中的河流构成了标志性的生态系统，这些生态系统受到多种人为压力的高度威胁。然而，这种压力组合使得制定和完善保护和恢复策略变得困难。因此，迫切需要获得更多关于普遍压力对鱼类种群，特别是像欧洲红点鲑（Thymallus thymallus）这样的指示物种的影响和相互作用的详细知识。在这里，我们进行了一项多河流、多压力源的调查，以分析灰鳟的种群状况。我们使用探索性决策树方法，梳理了四个主要压力源组的主要和交互作用：水流变化（即水跃）、渠道化、破碎化和水质变化。此外，我们使用改进的自举法，即汇集自举，确定了足够描述鱼类种群状况的最佳特征数量。在我们的数据集，水跃对灰鳟种群的影响最强。在水文控制站点，灰鳟的生物量大约是受水跃影响站点的八倍。预测种群状况的主要参数是下降率和峰值幅度，临界范围分别为 0.2-0.4 cm min 和 10-25 cm。在水跃河流中，河流形态和连通性是先前的次要参数。使用汇集自举数据集重复该过程，加强了这样的假设，即确定的参数在预测灰鳟种群状况方面最为相关。因此，基于生态阈值的水跃缓解是保护和恢复已经受到威胁的灰鳟种群的关键。在水跃河流中，高的河网连通性和异质的生境特征可以通过为鱼类的所有生命周期阶段提供庇护和栖息地来减轻脉冲流释放的不利影响。探索性树分析加上后验检验的方法，以及汇集自举方法，为研究人员和管理者提供了一个简单的框架，用于分析多因素数据集并得出可靠的管理结论。
