The Asian clam (Corbicula fluminea) is one of the rapidly spreading, very successful aquatic invasive species, which has become established widely in many parts of the world. Its spread is assumed to be by both passive and active dispersal. However, the importance of active pedal movement in dispersal is hardly known. Since there was no direct evidence of this phenomenon, field observations were combined with laboratory experiments to find out if the clams move upstream actively, and how this is affected by the quality of the substrate, the density of the clams, and the water velocity. Field observations were conducted at a small watercourse with no waterborne transport. Experiments were done in an indoor artificial stream system, where the distances moved by adult clams were measured via digital image analysis. Substrate grain size, starting density of clams, and water velocity significantly affected clam movement. Fine grain sediment and slow flow velocity both facilitated spread, while there was no clear pattern of density-dependent dispersal. Also, we found no clear preference for either upstream or downstream movement. The maximum distance moved in the lab experiments predicts no more than 0.15 km/y active pedal movement in an upstream direction, while our field observations detected a much faster (0.5–11 km/y) upstream movement, which might be explained by passive dispersal, such as via human transport and ecto- or endozoochory. Overall, it seems that active movement of the species cannot read to long-distance migration.

亚洲蛤（（Corbicula fluminea）是一种迅速传播的，非常成功的水生入侵物种之一，已在世界许多地方广泛建立。假定其扩散是通过被动和主动扩散进行的。然而，主动踏板运动在分散中的重要性几乎不为人所知。由于没有这种现象的直接证据，因此将野外观察与实验室实验相结合，以确定蛤if是否主动向上游移动，以及底物的质量，蛤the的密度和水流速如何影响蛤lam。实地观察是在没有水运的小河道上进行的。实验在室内人工流系统中进行，其中成年蛤moved移动的距离通过数字图像分析进行了测量。底物粒度，蛤starting的起始密度，和水流速度显着影响蛤的运动。细颗粒沉积物和缓慢的流速都促进了扩散，而没有清晰的依赖密度的扩散方式。另外，我们没有明显的偏好上游或下游运动。在实验室实验中，最大移动距离预测上游方向的主动踏板运动不会超过0.15 km / y，而我们的现场观察发现上游方向的主动踏板运动更快（0.5–11 km / y），这可以用被动分散来解释，例如通过人类运输以及体外或内吞。总体而言，该物种的活跃运动似乎无法理解为远距离迁移。我们没有明显的偏好上游或下游运动。在实验室实验中，最大移动距离预测上游方向的主动踏板运动不会超过0.15 km / y，而我们的现场观察发现上游方向的主动踏板运动更快（0.5–11 km / y），这可以用被动分散来解释，例如通过人类运输以及体外或内吞。总体而言，该物种的活跃运动似乎无法理解为远距离迁移。我们没有明显的偏好上游或下游运动。在实验室实验中，最大移动距离预测上游方向的主动踏板运动不会超过0.15 km / y，而我们的现场观察发现上游方向的主动踏板运动要快得多（0.5-11 km / y），这可以用被动分散来解释，例如通过人类运输以及体外或内吞。总体而言，该物种的活跃运动似乎无法理解为远距离迁移。例如通过人类运输以及体外或内吞。总体而言，该物种的活跃运动似乎无法理解为远距离迁移。例如通过人类运输以及体外或内吞。总体而言，该物种的活跃运动似乎无法理解为远距离迁移。