Lai Sum Yi, Pálsson Arnar, Guðbergsson Guðni, Jónsson Ingi Rúnar, Ólafsson Jón S, Bárðarson Hlynur
Marine and Freshwater Research Institute, Hafnarfjördur, Iceland.
University of Iceland, Reykjavík, Iceland.
J Fish Biol. 2024 Jul;105(1):72-84. doi: 10.1111/jfb.15757. Epub 2024 Apr 17.
The availability of resources varies across a species distributional range, and a low-productivity area can make a species more vulnerable. We investigated the invertebrate composition and prey choice of juvenile Atlantic salmon (Salmo salar L.) in low-productivity rivers in northeast Iceland, which is one of the species' most northerly distributions. By sampling benthic and drift invertebrate populations, we found that prey availability was similar within and between rivers. Gut content samples showed that the main prey choice for juvenile S. salar was the Chironomidae. The type of food items consumed varied across different weight groups of S. salar, with smaller juveniles having more diverse diet. S. salar did not have a selection preference for chironomids, which indicates that they were eating the highly available prey in their environment, rather than hunting high biomass items such as terrestrial invertebrates and large Dipterans. Estimates of dietary niche showed that S. salar in these low-productivity rivers relied on consuming what was most readily available, the chironomids, and that they must share resources with other salmonid species. This may be due to the low diversity of freshwater invertebrates (fewer prey options), whereas S. salar in nutrient-rich rivers could rely more on terrestrial invertebrates as an additional subsidy in their diet. In conclusion, with limited prey choices, juvenile S. salar in nutrient-poor rivers, especially in a biogeographically isolated region with low species diversity, may increase in vulnerability and decrease in adaptability to environmental change. Management methods that increase benthic prey abundance and diversity are recommended for conserving the S. salar population in a nutrient-poor river.
资源的可利用性在一个物种的分布范围内各不相同，而低生产力地区会使一个物种更易受到影响。我们调查了冰岛东北部低生产力河流中幼年大西洋鲑（Salmo salar L.）的无脊椎动物组成和猎物选择，该地区是该物种最靠北的分布区域之一。通过对底栖和漂流无脊椎动物种群进行采样，我们发现不同河流内部以及不同河流之间的猎物可利用性相似。肠道内容物样本显示，幼年大西洋鲑的主要猎物选择是摇蚊科。所消耗食物种类在不同体重组的大西洋鲑中有所不同，较小的幼鱼饮食更为多样。大西洋鲑对摇蚊没有选择偏好，这表明它们食用的是其环境中易于获取的猎物，而非捕食诸如陆生无脊椎动物和大型双翅目昆虫等高生物量的猎物。饮食生态位估计表明，这些低生产力河流中的大西洋鲑依赖于消耗最容易获得的摇蚊，并且它们必须与其他鲑科物种共享资源。这可能是由于淡水无脊椎动物多样性较低（猎物选择较少），而营养丰富河流中的大西洋鲑在饮食中可以更多地依赖陆生无脊椎动物作为额外的食物来源。总之，由于猎物选择有限，营养贫乏河流中的幼年大西洋鲑，尤其是在生物地理上隔离且物种多样性低的地区，可能会增加其脆弱性并降低对环境变化的适应能力。建议采用增加底栖猎物丰度和多样性的管理方法来保护营养贫乏河流中的大西洋鲑种群。
