Two female barbel Rarbus barbus (L.) were tagged with implantable radio transmitters and tracked in the Ourthe River (Southern Belgium) from April 12th to July 7th, 1989 to study their movements and activity rhythms during the spring-summer period. Both barbels defined a
1.6 km home range and occupied four residence areas. Greatest average daily movements within
the home range limits occurred during the prespawning and spawning periods and were associated
with variations of mean daily water temperature and level. Barbel 2 made a 9.6 km excursion from its spring home range and homed a week later in its residence area. Barbels displayed dusk and dawn
activity patterns, character- ized by the occupation of riffle areas. The activity timing was found to be dependent on water temperature while the size of daily activity area was more influenced by
river flow conditions.