Movement patterns of juvenile and adult noble crayfish (Astacus astacus) in a small stream, determined by radiotelemetry

This article reports on the results of the first radiotelemetric field study comparing the movement patterns of juvenile and adult noble crayfish (Astacus astacus) over the 24-h cycle. During our study (in summer, outside the reproduction period), juveniles moved over significantly longer distances than adults; upstream movements prevailed in both groups. The longest distance covered by an individual crayfish during a three-hour interval was 110 m (in the upstream direction). Adults moved most frequently at dusk and least frequently during daytime. Among juveniles, the likelihood of movement did not significantly differ between the times of day; however, distances covered by juveniles were the longest at night and significantly shorter during daytime and at dusk. Juveniles and adults exhibited very similar local activity (motion within a single place) with high values at night and low values during daytime.