Over time, humans have contributed to the loss of native species and have introduced non-native species throughout Europe. A new analysis shows how European freshwater fish have changed profoundly since 1840. At the continental scale, the contemporary fauna holds net 11 more species today as exotic species introduction (26 species) exceeded native species loss (15 species). But the biggest change was made by European species introduced from one area in Europe to another (77 species), often with fatal results.