Seasonal Shifts in Day-Time Resource Use of 0+ Barbel, Barbus Barbus

Abstract

Habitat preference and diet of 0+ barbel were studied both on a meso- and a microhabitat scale in the River Sieg (Germany) between May 1993 and January 1995. Changes in mesohabitat use were observed. Barbel moved from shallow bays (larvae and step 1 juveniles) to gravel banks, and subsequently, to riffles (step 2 juveniles). Size-dependent shifts in microhabitat-use were observed during the second juvenile step. These juveniles left the shoreline and preferred microhabitats with stronger current velocities. 0+ barbel in riffles fed on Chironomidae and Ephemeroptera. No remarkable shifts in diet were detected between larvae and juveniles. We suggest that the observed ontogenetic shifts to habitats with high food supply and low predation pressure might contribute to the high abundances of barbel in the River Sieg.