Ponto-Caspian gobies have invaded many river systems in the northern hemisphere, but their colonization patterns often remain unrecognized at the early stages of invasion. Here, we analyzed the ongoing invasion of the round goby Neogobius melanostomus (Pallas, 1814) in the Elbe River (Germany) by combining literature research with electrofishing and environmental DNA (eDNA) sampling. Along the surveyed 517 km, abundances peaked in the upper and lower sections, while low or no goby abundances were detected in the middle section. Combining the results of the field survey and literature data, we inferred four dispersal modes, jointly appearing during the colonization. (1) Human mediated transport, which was responsible for the initial colonization of the tidal Elbe and for a jumpy expansion to the upstream sections. (2) Fast downstream colonization, which was particularly observed for juvenile individuals. (3) Slow upstream migration, which was also recorded for another goby species, the bighead goby Ponticola kessleri (Günther, 1861) and (4) Lateral invasion via a major shipping canal in the middle river section. The eDNA analyses generally supported these conclusions and showed a high sensitivity and thus increased detection strength at low goby densities. Our study showed that the location of the first occurrence, as well as the dispersal mode, strongly determines the invasion process of non-native gobies.

Ponto-Caspian虾虎鱼已经入侵北半球的许多河流系统，但是在入侵的早期阶段，它们的定殖模式常常仍然未被人们所认识。在这里，我们分析了圆形虾虎鱼Neogobius melanostomus的持续入侵（Pallas，1814年），通过将文献研究与电钓鱼和环境DNA（eDNA）采样相结合，在易北河（德国）中进行。沿着被调查的517公里，在上段和下段的丰度达到峰值，而在中段则未发现虾虎鱼丰度低或没有。结合野外调查的结果和文献资料，我们推断出在殖民化过程中共同出现的四种传播方式。（1）人类介导的运输，这是潮汐易北河最初定居的原因，也是向上游地区迅速扩展的原因。（2）快速下游定植，在未成年个体中尤为明显。（3）上游迁移缓慢，另一只虾虎鱼也有记录，the虾虎鱼Ponticola kessleri（Günther，1861年）和（4）通过中间河段的一条主要航运运河进行侧向入侵。eDNA分析通常支持这些结论，并显示出高灵敏度，因此在低虾虎鱼密度下提高了检测强度。我们的研究表明，首次发生的位置以及扩散模式强烈地决定了非本地虾虎鱼的入侵过程。