1The killer shrimp (Dikerogammarus villosus) is one of the most recent, but also most 1 2 damaging, aquatic invasive species in Europe, but information on how the species responds 1 3 to novel predation pressures in recently invaded areas is very limited. We employed an open 1 4 test arena to examine predator recognition and anti-predatory behaviour in killer shrimp 1 5 exposed to either blank water or water conditioned with fish kairomones to simulate a 1 6 predator threat. Within five years after their introduction, killer shrimp spent much more time 1 7 hiding in the presence of fish kairomones than when they were exposed to blank water.