Bartram's Bass Micropterus sp. cf. cataractae is a rare black bass endemic to the Savannah River of the south-eastern United States and is threatened by habitat degradation and hybridisation with nonnative Alabama Bass Micropterus henshalli. While Bartram's Bass has been functionally extirpated from reservoirs, some populations persist in tributaries. Understanding the mechanisms affecting hybridisation in streams will help to inform conservation. Our objectives were to (a) compare spawning microhabitat use of Bartram's Bass between pure and hybridised individuals, (b) infer pure and hybridised spawning based on assessment of young-of-year (YOY) individuals, and (c) compare abiotic variables between sites where pure YOY Bartram's Bass were collected and where they were not collected. We snorkelled 27 sites in 2017 and 2018, recording microhabitat variables at each nest and at randomly selected paired locations. We then electrofished for YOY bass later in the summer. We found that Bartram's Bass selected for slower current velocities but not depths when spawning. Bartram's Bass nested on a variety of substrates associated with slow current velocity. Microhabitat variables did not differ between nests with pure individuals and those with hybrids; differences in tributary spawning habitat use are not likely to prevent hybridisation. We found widespread hybridisation in tributaries across the basin. Compared with sites where hybrid YOY were detected, sites with pure Bartram's Bass were in watersheds and local catchments that were more forested and less developed, and were higher in elevation with steeper gradients. Maintaining habitat integrity in locations where pure populations remain may help protect this rare species.

中文翻译：

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在萨凡纳河支流中筑巢微生境的使用和特有的Bartram鲈鱼的杂交

Bartram的低音Micropterus sp。cf. 白内障是美国东南部萨凡纳河特有的稀有黑鲈，受到栖息地退化和与非本地阿拉巴马州鲈鱼Micropterus henshalli杂交的威胁。尽管Bartram的Bass已从水库中彻底消灭，但仍有一些种群留在支流中。了解影响河流杂交的机制将有助于保护生物。我们的目标是（a）比较纯种和杂种个体之间使用Bartram's Bass产卵的微生境，（b）根据年幼（YOY）个体的评估推断纯种和杂种产卵，以及（c）比较两种生收集纯YOY Bartram低音的地方和未收集它们的地方。我们在2017年和2018年对27个站点进行了浮潜，记录了每个巢穴和随机选择的配对位置的微生境变量。然后，我们在夏天的晚些时候以电鱼的方式钓到了鲈鱼。我们发现Bartram的Bass在生成时选择了较慢的当前速度，但没有选择深度。Bartram的低音嵌套在与缓慢电流相关的各种基板上。有纯个体的巢和有杂种的巢的微生境变量没有差异。支流产卵栖息地使用方式的差异不太可能阻止杂交。我们在整个盆地的支流中发现了广泛的杂交。与检测到杂种YOY的地点相比，具有纯Bartram低音的地点位于流域和局部集水区，这些地区的森林茂密，发育程度较低，并且海拔较高且坡度更高。在仅有纯种群的地方保持栖息地的完整性可能有助于保护这种稀有物种。有纯个体的巢和有杂种的巢的微生境变量没有差异。支流产卵栖息地使用方式的差异不太可能阻止杂交。我们在整个盆地的支流中发现了广泛的杂交。与检测到杂种YOY的地点相比，具有纯Bartram低音的地点位于流域和局部集水区，这些地区的森林茂密，发育程度较低，并且海拔较高且坡度更高。在仅有纯种群的地方保持栖息地的完整性可能有助于保护这种稀有物种。有纯个体的巢和有杂种的巢的微生境变量没有差异。支流产卵栖息地使用方式的差异不太可能阻止杂交。我们在整个盆地的支流中发现了广泛的杂交。与检测到杂种YOY的地点相比，具有纯Bartram低音的地点位于流域和局部集水区，这些地区的森林茂密，发育程度较低，并且海拔较高且坡度更高。在仅有纯种群的地方保持栖息地的完整性可能有助于保护这种稀有物种。低音位于流域和局部集水区，森林茂密，发育欠佳，且海拔较高且坡度较陡。在仅有纯种群的地方保持栖息地的完整性可能有助于保护这种稀有物种。低音位于流域和局部集水区，森林茂密，发育欠佳，且海拔较高且坡度较陡。在仅有纯种群的地方保持栖息地的完整性可能有助于保护这种稀有物种。