Diel activity of adult pikeperch Sander lucioperca (L.) in a drainage canal in the Mediterranean basin during spring.

Pikeperch ( Sander lucioperca L.) is a broadly distributed fish species in Europe but little is known about its ecology in the southern part of its distribution area in warm climatic conditions. The aim of this study was to analyse pikeperch rate of movement and to assess whether it displayed a diel pattern related to temperature. Thus acoustic telemetry was used to track adult pikeperch in a drainage canal located in south of France. The survey was carried out in spring, during the spawning period. The results showed that females were more active than males. This is in accordance with previous data on the nest guardian behaviour of the males. For both genders, the activity rates increased during the study period as water temperature rose. Males and females displayed the same diel activity with a maximum at dusk, thereby confirming many indirect observations. Nevertheless, inter-individuals variations were observed. Thus, these results on diel activity are rather a general trend than a strict rule and suggest the involvement of other factors than light intensity in the control of diel activity. This diel rhythm is positively correlated to water temperature for females. Pikeperch activity may be the result of a trade-off between physiological requirements of temperature and light, satisfaction of energy needs and avoidance of predators. [ABSTRACT FROM AUTHOR]