The monkey goby, an invasive Ponto-Caspian species, recently extended its range to the west and north in the Vistula River system. Dispersal of the monkey goby upstream in this river system to its Carpathian tributaries was not expected to occur due to its habitat preferences. Preferring slow- to medium-running rivers with sandy substrates, the conditions in submountain rivers with fast water currents and coarse-grained bottom substrates probably prevented the monkey goby from expanding. However, the long periods of low discharge, which recently became frequent in the Carpathians, caused a significant part of the riverbeds to have shallow sections with slow-flowing water. This could have been an impulse to launch a “second wave of invasion” of the monkey goby in the Vistula River system. Catch data from 2022, indicated that the range of the monkey goby expanded by ~ 80 km upstream of the Vistula River and ~ 260 km upstream in the San River compared to previous catch data. The findings in the San River are the first known locations of this species in the Carpathians. Under the assumption that low water levels in the Carpathian rivers will continue to occur in the coming years, the monkey goby may increase its numbers and become dominant in the sections near the banks of these submountain rivers, which are also the habitats of native fish fry.

猴虾虎鱼是一种入侵滨里海物种，最近将其活动范围扩大到维斯瓦河系统的西部和北部。由于猴虾虎鱼的栖息地偏好，预计不会发生该河流系统上游至喀尔巴阡支流的猴虾虎鱼的扩散。猴虾虎鱼喜欢流淌缓慢至中流且底质为沙质的河流，而山下河流中水流湍急且底部底质粗粒的条件可能会阻止猴虾虎鱼的扩张。然而，近期在喀尔巴阡山脉频繁出现的长期低流量导致大部分河床出现水流缓慢的浅水区。这可能是虾虎鱼在维斯瓦河水系发起“第二波入侵”的冲动。 2022 年的渔获量数据表明，与之前的渔获量数据相比，猴虾虎鱼的活动范围在维斯瓦河上游扩大了约 80 公里，在桑河上游扩大了约 260 公里。圣河的发现是该物种在喀尔巴阡山脉的第一个已知地点。假设喀尔巴阡山脉河流的低水位在未来几年将继续出现，猴虾虎鱼的数量可能会增加，并在这些山下河流沿岸附近的地区占据主导地位，这些地区也是本地鱼苗的栖息地。