Water level variation has an important role in the biology of fish species, driving behavior, feeding, and reproduction both in natural and modified environments. In reservoirs, different dam operation schemes result in alternative patterns of water level fluctuations. Storage (STR) reservoirs accumulate water and can vary the water level unpredictably, whereas this variation is more discrete in run-of-river (ROR) reservoirs. For this reason, ROR reservoirs are commonly presumed to be less environmentally harmful than STR reservoirs. We used multivariate autoregressive models (MAR) to compare the stability and species interactions of fish assemblages from two reservoirs under alternative operation schemes, using long-term data (15 years). We hypothesized that the lower variability of water level in the ROR reservoir would coincide with a more stable fish assemblage than in the STR reservoir. Contrary to our expectation, the MAR properties related to resilience and resistance indicated that the fish assemblage from the ROR was less stable than that from the STR reservoir. This suggests that the absence of water level variation limits the potential direct (movement and reproduction of fish) and indirect (primary production and nutrient input) benefits for fish that arise from the temporal environmental heterogeneity. Most importantly, this study highlights the need to reexamine the implications of ROR reservoirs on the health of aquatic communities. At least for fish, management actions should include varying the water level in a regime as similar as possible to the natural flow regime of the river, in order to improve the state of assemblages.

中文翻译：

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蓄水或径流水库：探索大坝运行对鱼类组合稳定性和物种相互作用的生态影响

水位变化对自然环境和改良环境中鱼类物种的生物学、驱动行为、摄食和繁殖具有重要作用。在水库中，不同的大坝运营方案会导致水位波动的不同模式。蓄水 (STR) 水库会积水，并且可以不可预测地改变水位，而这种变化在径流 (ROR) 水库中更为离散。出于这个原因，通常认为 ROR 储层比 ​​STR 储层对环境的危害更小。我们使用多变量自回归模型 (MAR) 使用长期数据（15 年）来比较不同操作方案下两个水库鱼类组合的稳定性和物种相互作用。我们假设 ROR 水库中较低的水位变化与比 STR 水库中更稳定的鱼类组合相吻合。与我们的预期相反，与弹性和抵抗力相关的 MAR 特性表明，来自 ROR 的鱼群不如来自 STR 水库的鱼群稳定。这表明没有水位变化限制了时间环境异质性对鱼类的潜在直接（鱼类的移动和繁殖）和间接（初级生产和营养输入）利益。最重要的是，这项研究强调需要重新审视 ROR 水库对水生社区健康的影响。至少对于鱼来说，