Turbidity increases behavioural diversity in northern pike, Esox lucius L., during early summer

Optimal behavioural strategies of aquatic organisms may change with environmental conditions such as turbidity. It was hypothesised that pike, Esox lucius L., adapts to low visibility and potential-reduced foraging opportunities by an increase in activity and pelagic residence in turbid conditions. Diel activity and habitat use of pike (57-85 cm) were studied in a turbid lake and a clear-water lake by tracking 31 radio-tagged pike during two diurnal tracking sessions in June 2006. A significant interaction between lake and total length of pike was found, suggesting a higher activity level in large pike in the turbid lake. In addition, pike exhibited a higher among-individual variance in movement and habitat use in the turbid lake. These results suggest a higher degree of behavioural diversity in pike in the turbid lake as a response to low visibility and a resulting change in foraging conditions.