Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden.
WasserCluster Lunz-Inter-University Centre for Aquatic Ecosystem Research, Lunz am See, Austria.
J Fish Biol. 2022 Apr;100(4):1033-1043. doi: 10.1111/jfb.15010. Epub 2022 Mar 1.
Interference competition over food and territory can shape population structure and habitat use within and between species. The introduction of invasive species often leads to novel competitive interactions over shared resources and invaders can eventually exclude the native species from preferred habitats. Invasive brook trout (Salvelinus fontinalis) introduced to northern Europe have excluded native brown trout (Salmo trutta) from numerous headwater streams. The fact that invasive brook trout can displace the more aggressive brown trout is puzzling. However, the earlier spawning and hatching of brook trout, compared to brown trout, may lead to unequal competition due to size advantage and prior resident status of brook trout at the fry stage. In this study, we examine the effect of competition between brown trout and brook trout using the natural size distribution of the two species. In two consecutive experiments, we first measured space use and feeding of a fry (age 0+) in the presence of a juvenile (age 1+). In experiment 2, we assessed territorial interactions between the species at the fry stage (age 0+) and if smaller brown trout could compensate the disadvantage by manipulating residence duration. Fry of brook trout feed sooner and spend more time close to the larger individual than brown trout fry. We also found that brook trout fry won most territorial contests against brown trout, and that increased residence duration led to longer and more aggressive interactions. The results suggest that smaller brown trout are displaced to suboptimal habitats in the presence of a larger brook trout. Therefore, the later emergence from gravel beds resulting in the naturally occurring size disadvantage of brown trout at the fry stage may lead to unequal territorial interactions that could explain why brown trout are displaced from preferred habitats in sympatry with brook trout.
食物和领地的竞争会影响物种内部和物种之间的种群结构和栖息地利用。入侵物种的引入通常会导致对共享资源的新的竞争，而入侵者最终可能会将本地物种从偏好的栖息地中驱逐出去。在北欧引入的入侵性虹鳟（Salvelinus fontinalis）已经将本地的褐鳟（Salmo trutta）从许多上游溪流中排挤出去。虹鳟能够取代更具攻击性的褐鳟这一事实令人费解。然而，与褐鳟相比，虹鳟更早的产卵和孵化可能会导致大小优势和虹鳟在鱼苗阶段的先驻留地位导致不平等竞争。在这项研究中，我们使用这两个物种的自然大小分布来研究褐鳟和虹鳟之间的竞争效应。在两个连续的实验中，我们首先测量了在幼鱼（年龄 1+）存在的情况下，鱼苗（年龄 0+）的空间利用和摄食情况。在实验 2 中，我们评估了物种在鱼苗阶段（年龄 0+）的领地相互作用，以及较小的褐鳟是否可以通过操纵居留时间来弥补劣势。与褐鳟鱼苗相比，虹鳟鱼苗更早开始进食，并且更多时间靠近较大个体。我们还发现，虹鳟鱼苗在大多数与褐鳟的领地竞争中获胜，并且增加居留时间会导致更长时间和更具攻击性的相互作用。结果表明，在较大的虹鳟存在的情况下，较小的褐鳟会被驱逐到次优栖息地。因此，在自然发生的褐鳟在鱼苗阶段的大小劣势中，从砾石床中更早出现的结果可能会导致不平等的领地相互作用，这可以解释为什么在与虹鳟共存时，褐鳟会从偏好的栖息地中被驱逐。
