Collaborative research--Terrestrial Effects of an Aquatic Invader: Does Regional Context Change the Impact of Fish Invasion on Energy Flow to Riparian Predators?

生物入侵是世界范围内物种迅速消失的两个主要原因之一，预计到本世纪末，生物入侵可能导致三分之二的物种消失。外来物种的入侵不仅会产生直接影响（竞争、捕食），还会通过食物网和其他生态系统产生间接影响。例如，日本最近的研究表明，外来入侵的虹鳟鱼对河流食物网的间接影响减少了从河流中出现的成年水生昆虫的数量，并导致河边蜘蛛的数量下降了65%。推而拓展，河边的鸟类也从新出现的昆虫中获得大约25%的能量，所以入侵的鳟鱼也会影响它们。这个项目将研究外来的鳟鱼入侵对落基山脉溪流的影响，这是一种更广泛的入侵，影响了数千英里的溪流。这项研究将测试这些鱼类入侵者是否对本地切喉鳟鱼有类似的直接影响，就像虹鳟鱼对日本本地鱼类的影响一样。它还将研究这些影响是否会通过河流食物网传播，并减少以河边蜘蛛为食的水生昆虫的出现。这些影响将通过使用稳定的氮同位素直接或间接测量。这项工作将在从落基山脉中部到北部的溪流中进行，在这些溪流中，非本土小溪鳟鱼被移走，并与它们入侵的地方进行比较。这项研究将对这些河流系统的渔业管理产生实际影响。

Biological invasions are one of two main causes of the rapid loss of species worldwide, and may contribute to the predicted loss of two-thirds of all species by the end of this century. Invasions of nonnative species not only have direct effects (competition, predation), but also indirect effects that cascade through food webs and into other ecosystems. For example, recent research in Japan showed that the indirect effects of nonnative invading rainbow trout on stream food webs reduced the amount of adult aquatic insects emerging from the stream and caused a 65% decline in streamside spiders. By extension, streamside birds also gain about 25% of their energy from emerging insects, so invading trout could affect them as well. This project will study the effect of nonnative brook trout invasions in Rocky Mountain streams, an even more widespread invasion that affects thousands of stream miles. This study will test whether these fish invaders have similar direct effects on native cutthroat trout as rainbow trout do on native fish in Japan. It will also examine whether these effects propagate through the stream food web and reduce emerging aquatic insects that feed streamside spiders. These effects will be measured directly and indirectly by using a stable isotope of nitrogen. This work will be performed in stream sections where nonnative brook trout are removed and compared to those where they have invaded, and along a gradient from central to northern Rocky Mountain streams. This study will have applied implications for the fisheries management of these stream systems.