Until recently, Belgium was spared from the establishment of Asian weatherfishes, globally spreading IAS by intentional and unintentional spillover from the food and aquarium trade. In spring 2019 however, some individuals were captured in a small pond in a nature reserve close to an area across the border with The Netherlands where a proliferating population was already known to exist since at least 2012. This species was formerly regarded as the in Europe already well-established oriental weatherfish (Misgurnus anguillicaudatus Cantor 1842) but genetic analysis identified it as the northern weatherfish (M. bipartitus Sauvage & Dabry de Thiersant 1874), officially still treated as a younger synonym of the Amur weatherfish (Misgurnus mohoity Dybowski 1869). Both a larger scale eDNA survey followed by a well-targeted fishing campaign (fyke nets, electric fishing) showed that the species is rapidly spreading from the area of first detection and revealed that it is already occurring at high abundances. As such, it is penetrating one of the last remaining strongholds of the European weatherfish (M. fossilis L. 1758) in Belgium, a protected species under the European Habitats Directive (Appendix II). Competitive exclusion, hybridisation and transfer of non-native diseases may consequently pose a serious threat to this enigmatic swamp inhabitant. Preliminary testing with small double fyke nets revealed high catches of the northern weatherfish (>100 ind./fyke) and a specific fishery campaign on strategic locations was launched in 2021 as an Early Detection Rapid Response (EDRR) measure to repress their numbers and further spread. Habitat rehabilitation in combination with ex-situ breeding of European weatherfish and release of sterile northern weatherfish individuals are however prime measures that should help turn the tide in favour of the native weatherfish, but these largely depend on/await European subsidies.