The Sickle Darter Percina williamsi (Page and Near, 2007) is a species of fish endemic to the upper Tennessee River basin in eastern Tennessee, southwestern Virginia, and western North Carolina. Because of its narrow range and presumed decline in occupied sites over the last half century, it is being proposed for federal listing under the Endangered Species Act. We analyzed the current distribution of the Sickle Darter and temporal trends in its distribution in relation to temporal trends in environmental and habitat covariates for each of the historically occupied sub-basins (upper Clinch, Emory, upper French Broad, Little, Little Pigeon, Middle Fork Holston, North Fork Holston, Powell, South Fork Holston, and Watauga) with multiple linear regression modelling. A total of 154 Sickle Darters were observed at 15 sites throughout the upper Tennessee River Basin. Sickle Darters were observed in the Little River, Emory River, and Middle Fork Holston River sub-basins. A total of 133 unique historical occurrences were used for the spatiotemporal analyses. Sickle Darters have declined in 8 out of 10 historically occupied sub-basins. Our best model for the whole distribution scale (Mallow's Cp = −0.87; Adjusted R² = .92) suggests that habitat fragmentation due to damming has had adverse effects on Sickle Darter populations across its distribution. Models were very similar for the sub-basin specific models as well. The results from this study highlight the drivers of decline in Sickle Darter distribution and outline the future research needs for this species that should be used to inform future conservation decisions regarding this species.

中文翻译：

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田纳西河流域上游 Sickle Darter (Percina williamsi Page and Near, 2007) 分布的时空评估

镰刀镖Percina williamsi(Page and Near, 2007) 是田纳西州东部、弗吉尼亚州西南部和北卡罗来纳州西部田纳西河流域上游的一种特有鱼类。由于其范围狭窄且在过去半个世纪中被占用的地点据推测有所减少，因此正在提议根据《濒危物种法》将其列入联邦名单。我们分析了 Sickle Darter 的当前分布及其与环境和栖息地协变量的时间趋势相关的分布的时间趋势，这些趋势与每个历史上被占用的子盆地（上克林奇、埃默里、上法国布罗德、小、小鸽子、中Fork Holston、North Fork Holston、Powell、South Fork Holston 和 Watauga）与多元线性回归建模。在整个田纳西河流域上游的 15 个地点共观察到 154 只镰刀镖。在 Little River、Emory River 和 Middle Fork Holston River 子流域观察到 Sickle Darters。总共使用了 133 个独特的历史事件进行时空分析。Sickle Darters 在 10 个历史上有人居住的子盆地中有 8 个下降。我们针对整个分销规模的最佳模型（Mallow's Cp  = -0.87；调整后的R ²  = .92) 表明由于筑坝造成的栖息地破碎化对整个分布的镰刀镖种群产生了不利影响。子流域特定模型的模型也非常相似。这项研究的结果突出了镰刀镖分布下降的驱动因素，并概述了对该物种的未来研究需求，这些需求应用于为有关该物种的未来保护决策提供信息。