Aquatic parasites cause disease in economically and culturally important Klamath River salmonids Oncorhynchus spp., and the myxozoan parasite Ceratonova shasta has been linked to high juvenile salmonid mortality. Because C. shasta requires the freshwater annelid Manayunkia occidentalis to complete its life cycle, management approaches have focused on disrupting annelid populations to reduce C. shasta and disease risk for salmonids. Previous studies have demonstrated that manipulating river discharge to achieve short-term, high-flow events is effective for disturbing annelids. There is also interest in the efficacy of manipulating river discharge to desiccate annelids to reduce disease risk. To investigate the efficacy of reducing streamflow to desiccate annelids, we simulated the amount of annelid habitat, categorized by quality, that would be dewatered as discharge was incrementally reduced. Simulations were accomplished by coupling two-dimensional hydrodynamic models with an annelid presence/absence model. Simulations were conducted for three study sites located on the Klamath River main stem downstream of Iron Gate Dam, where discharge can be manipulated. Reductions in discharge from June base flow (31.2 m³/s or 1,100 ft^3/s) to the lowest simulated discharge rate (17.0 m³/s; approximately half of base flow) resulted in an 11.8% reduction of the total wetted area of the river across all three study sites combined. For the same discharge simulation, reductions in annelid habitat differed based on the quality of habitat, with low- quality (<0.20 probability of annelids) to moderate-quality (0.20–0.80 probability of annelids) habitat reduced by 8.3% (95% credible interval = 7.5–10.3) and 23.7% (10.7–27.5), respectively, while high-quality habitat (>0.80 probability of annelids) was never desiccated. These results suggest that desiccation is unlikely to offer an effective solution for managing myxozoan parasites of salmonids that are transmitted by annelids because reducing streamflow had minimal effects on the amount of annelid habitat.

中文翻译：

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减少河流流量以控制克拉马斯河的寄生鲑鱼病：模拟质疑干燥作为管理工具的功效

水生寄生虫在具有重要经济和文化意义的克拉马斯河鲑鱼Oncorhynchus spp. 中引起疾病，粘虫寄生虫Ceratonova s​​hasta与高幼年鲑鱼死亡率有关。由于Ç。shasta需要淡水环节动物Manayunkia occidentalis来完成其生命周期，管理方法的重点是破坏环节动物种群以减少C。沙斯塔和鲑鱼的疾病风险。先前的研究表明，操纵河流流量以实现短期高流量事件对干扰环节动物是有效的。也有人对操纵河流流量以干燥环节动物以降低疾病风险的功效感兴趣。为了研究减少水流使环节动物干燥的功效，我们模拟了环节动物栖息地的数量，按质量分类，随着排放量的逐渐减少，这些栖息地将被脱水。通过将二维流体动力学模型与环节动物存在/不存在模型耦合来完成模拟。对位于铁门大坝下游克拉马斯河主干上的三个研究地点进行了模拟，在那里可以操纵排放。6 月基流（31.2 m ³/s 或 1,100 ft ^3/ s) 到最低模拟排放速率 (17.0 m ³/s; 大约一半的基流）导致所有三个研究地点的河流总润湿面积减少了 11.8%。对于相同的排放模拟，环节动物栖息地的减少因栖息地质量而异，低质量（环节动物的概率<0.20）到中等质量（环节动物的概率为 0.20-0.80）的栖息地减少了 8.3%（95% 可信）间隔 = 7.5–10.3) 和 23.7% (10.7–27.5)，而优质栖息地（环节动物的概率 >0.80）从未干燥。这些结果表明，干燥不太可能为管理由环节动物传播的鲑科动物粘液动物寄生虫提供有效的解决方案，因为减少流量对环节动物栖息地数量的影响很小。