Anti-predator behaviour of naive compared with experienced juvenile roach

Juvenile roach Rutilus rutilus without any previous contact with predatory fishes reacted to the presence of alarm substances more intensively than fish with previous experience. Among several types of behavioural response observed, some, such as hiding, were not registered in experienced fish, The most pronounced difference between the two juvenile fish categories was manifested in feeding. Naive fish used more time for feeding than experienced ones. The experiment showed that alarm substance originating from small and young and medium roach induced a stronger reaction than the substance extracted from large and olden fish. (C) 2001 The Fisheries Society of the British Isles.