In a mesocosm experiment, we tested whether larval fish show an active behavioural response to hydrodynamic impacts. Exposing I to 3 week old allis shad (Alosa alosa) larvae to a pulsed wave regime, we found that already I week old larvae immediately adapt their microhabitat use and activity patterns at the onset of the wave pulses. The fish larvae in stantaneously increased their activity leve...