Fish stranding in rivers, due to rapid shoreline dewatering, often occurs during the down‐ramping phase of hydropeaks, which enables peak energy production. Multiple hydropeaking characteristics and river morphology influence stranding, but little is known about the effects of riverbed microstructures. Our goal was to identify how the combination of hydropeaking characteristics and the occurrence of morphological microstructures (e.g., puddles and scour pools) influences fish stranding. For this purpose, we used an extensive dataset of fish stranding observations collected over 3 years in spring at 48 sites along a 50 km‐long reach of the Ain River, France. We aimed (1) to characterize stranding events and their associated fish assemblages and (2) to identify the spatial and temporal determinants of stranding. The occurrence of morphological microstructures was the main factor explaining fish stranding. Scour pools had a strong impact, followed by scour puddles, humid zones, and alluvial puddles. Then, hydropeaking characteristics interacted with morphology and modulated the intensity of stranding. Low flow ranges (low peak flow and low base flow) occurring after periods without hydropeaks induced ‘salmonid fry’ stranding events and ‘super‐stranding’ events (massive stranding of many taxa). Other flow ranges induced ‘regular cyprinid fry’ stranding events. Salmonids were particularly subject to stranding at the beginning of the sampling period. Recommendations are (1) to act in priority on sites where stranding is most likely, by morphological operations or by installing attractive structures in the perennial area and (2) to maintain attractive, perennial habitats in the low flow range of hydropeaks, for example, by increasing base flow.

中文翻译：

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表征形态微结构和水峰对河流鱼类搁浅的影响

由于海岸线快速脱水，河流中的鱼类搁浅经常发生在水位峰值的下降阶段，这使得能量产生达到峰值。多重水峰特征和河流形态会影响搁浅，但人们对河床微观结构的影响知之甚少。我们的目标是确定水峰特征和微观形态结构（例如水坑和冲刷池）的结合如何影响鱼类搁浅。为此，我们使用了 3 年多来春季在法国安河 50 公里长河段沿线 48 个地点收集的鱼类搁浅观测数据集。我们的目标是（1）描述搁浅事件及其相关鱼类组合的特征，以及（2）确定搁浅的空间和时间决定因素。形态微结构的出现是造成鱼类搁浅的主要因素。冲刷池影响强烈，其次是冲刷水坑、潮湿区和冲积水坑。然后，水峰特性与形态相互作用并调节绞合强度。在没有水峰的时期之后发生的低流量范围（低峰值流量和低基流）引发了“鲑鱼苗”搁浅事件和“超级搁浅”事件（许多类群的大规模搁浅）。其他流量范围会引发“常规鲤科鱼苗”搁浅事件。鲑鱼在采样期开始时特别容易搁浅。建议 (1) 通过形态操作或在常年区域安装有吸引力的结构，优先在最有可能搁浅的地点采取行动；(2) 在水峰的低流量范围内维持有吸引力的常年栖息地，例如，通过增加基流。