Antipredator behaviour of 0+ year Perca fluviatilis:: effect of vegetation density and turbidity

In this study, the combined influence of vegetation density and water turbidity on habitat utilization of a prey Fish, 0+ year perch Perca fluviatilis, under predation risk (pike, Esox lucius) was investigated. The vegetated habitat was overall preferred over the open habitat in the presence of a predator. The level of turbidity, and to a lesser extent vegetation density, however, influenced the response of 0+ year perch. The use of the vegetated habitat was lower in very turbid than in clear and turbid conditions, suggesting reduced antipredator behaviour in very turbid water. The effect of vegetation density on antipredator behaviour was only present in clear water, where the use of a structural refuge decreased with increasing vegetation density. No such effect was observed in turbid and very turbid water. The results showed that the structuring role of vegetation or habitat complexity may diminish with increased turbidity. The observed masking effect of turbidity suggests that predator-prey interactions in vegetated habitats are more complex than what has generally been thought. (C) 2004 The Fisheries Society of the British Isles.