Drastic changes in the amphipod fauna (Crustacea) of Dutch inland waters during the last 25 years

After the introduction of Gammarus tigrinus in The Netherlands some 25 years ago and of other recently invading amphipods ( Crangonyx pseudogracilis and Corophium curvispinum ) the native species decreased, the invaders increased. The success of these invaders and its impact on the local amphipod fauna is discussed. Electrophoretic tests give evidence that a second invasion of Gammarus tigrinus , this time from Germany, is taking place. Some predictions about future developments are made.