Abstract Streams are complex systems that rely on connectivity to maintain natural ecological function. Low-water crossings are common in small-intermediate sized streams and can restrict longitudinal movement of fishes. The Current River in Missouri (USA) contains a single anthropogenic barrier to longitudinal connectivity: the Cedar Grove low-water crossing, which spans the main channel (10 culverts) and a side channel (4 culverts). In July 2017, we radio-tagged Northern Hog Sucker Hypentelium nigricans upstream (henceforth ‘above’; N = 24) and downstream (henceforth ‘below’; N = 26) of the crossing and followed their movements monthly for a year to assess fish passage and maximum displacement. Passage was limited to four below-tagged fish passing upstream of the crossing with one fish making an additional downstream and then upstream passage. Passage was more likely to occur during high flow. On average, below-tagged fish exhibited more than seven times greater maximum displacement (Mean (M) = 6.55 km, Standard Error (SE) = 2.91 km) than above-tagged fish (M = 0.92 km, SE = 0.33 km). The majority (71%) of fish exhibited stationary behavior (<1 km) compared to mobile behavior (>1 km). Among mobile individuals, maximum displacement was greatest away from the crossing, with above-tagged fish favoring upstream movements (100%) and below-tagged fish favoring downstream movements (67%). Our results suggest the crossing is a semi-permeable barrier in which fish passage primarily occurs during high flows. Alternatives to the low-water crossings at Cedar Grove should be considered to promote natural longitudinal movement of fishes. The side channel provides a potentially impactful and economically feasible management opportunity to act as a fish bypass channel on the Current River.

中文翻译：

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低水位穿越影响了奥扎克溪流中的北猪吸盘 Hypentelium nigricans 运动

摘要 河流是依赖连通性来维持自然生态功能的复杂系统。低水位穿越在中小型溪流中很常见，会限制鱼类的纵向移动。密苏里州（美国）的 Current River 包含一个纵向连通性的单一人为障碍：Cedar Grove 低水位交叉口，它跨越主航道（10 个涵洞）和一个侧航道（4 个涵洞）。2017 年 7 月，我们用无线电标记了北猪吸盘 Hypentelium nigricans 上游（以下称为“上方”；N = 24）和下游（以下称为“下方”；N = 26），并在一年内每月跟踪它们的运动以评估鱼类通道和最大位移。通道仅限于四条标记以下的鱼通过交叉口的上游，其中一条鱼通过额外的下游和上游通道。在高流量期间更可能发生通过。平均而言，低于标记的鱼表现出的最大位移（平均 (M) = 6.55 公里，标准误差 (SE) = 2.91 公里）是高于标记的鱼（M = 0.92 公里，SE = 0.33 公里）的七倍以上。与移动行为（> 1 公里）相比，大多数（71%）的鱼表现出静止行为（<1 公里）。在移动个体中，远离交叉点的最大位移最大，标记上方的鱼有利于上游移动 (100%)，标记下方的鱼有利于下游移动 (67%)。我们的结果表明，穿越是一个半渗透的屏障，其中鱼类通过主要发生在高流量期间。应考虑在 Cedar Grove 低水位穿越的替代方案，以促进鱼类的自然纵向运动。