Executive summary PROBABILITY OF ESTABLISHMENT AND SPREAD (EXPOSURE) Entry in Belgium It is very likely that Amur sleeper will enter Belgian waters in the near future if it were to be used as an aquarium fish. Especially fish transports from fish farms in infested areas (where Amur sleeper can be present as a stowaway) to local fish farms here may serve as an important entry pathway. From aquaculture ponds it may spread via escapes or through fish stocking activities. Establishment capacity Perccottus glenii is not yet present in Belgium or neighbouring, interconnected river systems. However, all literature indicates a high probability of future establishment in most parts of Belgium (especially Flanders with its standing and slow streaming waters). Dispersion capacity Human aided dispersal (aquarium trade and aquaculture) has helped Amur sleeper to invade large parts of Eurasia. Natural spread was probably the main vector for downstream dispersal. Because of high propagule pressure from high density populations in standing waters in flood plains, the importance of this last vector must not be underestimated in the widespread distribution of P. glenii. EFFECT OF ESTABLISHMENT Environmental impacts The environmental impacts of the presence of Amur sleeper in Belgium will be through competition for food and predation but also possibly through pathogen pollution and disruption of trophic interactions. Mainly native freshwater fish and amphibians will be affected but also (larvae of) large invertebrates will be heavily predated upon. Especially standing waters (oxbow lakes, ponds, etc.), where high densities of P. glenii can be expected, will be the ecosystems at risk. Other impacts In aquaculture facilities and in commercial fishing grounds, Amur sleeper may be a competitor for food and may thus reduce production of economically important fish species. Social impacts, however, have not been reported. CONCLUSION FOR RISK ASSESSMENT The Amur sleeper may easily reach Belgium as a stowaway of fish consignments and/or ...