The abundance of aquatic vegetation is increasing in rivers and lakes worldwide. The aim of this study was to find how the macrophyte Juncus bulbosus Linnaeus affects salmonids and benthic macroinvertebrates in Norwegian rivers. The proliferation of J. bulbosus in the study rivers commenced after the development of hydropower in the 1960s and 1970s. J. bulbosus is now considered a nuisance for humans in many areas of the rivers. We found a higher density of juvenile fish and higher density, weight and species richness of invertebrates in areas with J. bulbosus than in areas with gravel, suggesting that the vegetation is not limiting fish and invertebrates. This may be because macrophytes increase the surface area and provide shelter, food and a variety of ecological niches. Adult salmonid fish can be negatively affected when their spawning grounds are covered by vegetation. However, overgrowth is not common and may take years since fish clear the river bed of macrophytes during redd digging, indicating competition between macrophytes and fish for riverbed habitat. Our results suggest that one should not assume that outgrowths of macrophytes have negative impacts on the ecosystem. It is important to map all impacts and distinguish nuisance to humans from effects on the ecosystem.

世界范围内的河流和湖泊中，水生植物的丰度正在增加。这项研究的目的是发现大型植物Juncus bulbosus Linnaeus如何影响挪威河流域的鲑鱼和底栖大型无脊椎动物。1960年代和1970年代水电开发之后，研究河中的J. bulbosus开始扩散。如今，J。bulbosus在河流的许多地区都被认为是对人类的滋扰。我们发现在J. bulbosus地区，幼鱼的密度更高，无脊椎动物的密度，重量和物种丰富度更高比有砾石的地区要少，这表明植被并没有限制鱼类和无脊椎动物。这可能是因为大型植物增加了表面积并提供了庇护所，食物和各种生态位。成年鲑鱼的产卵场被植被覆盖时，可能会受到不利影响。但是，过度生长并不常见，可能需要数年的时间，因为鱼在冲积过程中会清除大型植物的河床，这表明大型植物和鱼类之间在河床栖息地方面存在竞争。我们的结果表明，不应假设大型植物的生长对生态系统有负面影响。重要的是要绘制所有影响并区分对人类的滋扰和对生态系统的影响。