East European crayfish stocks at risk: arrival of non-indigenous crayfish species

An increasing number of non-indigenous crayfish species (NICS) of apparently pet trade origin have become established particularly in Europe. Especially alarming are recent confirmation of two distantly separated marbled crayfish Procambarus fallax f. virginalis populations in Ukraine and indications of more North American cambarids present in the local pet market. The present study aimed to investigate crayfish species availability within the Ukrainian pet trade together with the climate match and risk they represent to the freshwater ecosystems generally and indigenous crayfish species in particular. Altogether, 15 NICS belonging to all three crayfish families were detected. Considering their origin, availability, probability of establishment, invasiveness and further aspects, marbled crayfish and red swamp crayfish Procambarus clarkii appear to be potentially the most troubling. Available information obtained from the pet trade in ornamental crayfish as a whole demonstrates that the broad availability of NICS most probably overlaps the vast majority of European indigenous crayfish species distribution, including the endemic thick-clawed crayfish Astacus pachypus, which occupies only a limited area that is situated critically close to established marbled crayfish populations. Negative effects of NICS on freshwater ecosystems as a whole can be also expected.