Qualitative and quantitative aspects of the diet of Barbus callensis Valenciennes, 1842, as well as its feeding rhythm, were investigated. Food varied according to the size and age of the fish, to the composition of the invertebrate fauna and to the hydrological phases of the biotopes. Young barbel ate algae and microzoobenthos, mostly larvae of Chironomidae and Simuliidae. Older specimens fed on larger benthos, such as larvae of Ephemeroptera and Trichoptera and on plant fragments; they captured small fishes when benthos became scarce. B. callensis fed during the day.  In young specimens this activity was lower during the winter, presumably because of low temperature and floods. In adults, feeding decreased in spring during the spawning period, when the fishes might even fast completely.