THE DIET OF RUDD, SCARDINIUS-ERYTHROPHTHALMUS AND ITS ROLE IN A BIOMANIPULATION EXPERIMENT IN LAKE-WIRBEL

In 1991, 63 alimentary canals of rudd Scardinius erythrophthalmus (L.) from 5.1 to 11.0 cm SL were analysed. The main food items were macrop hytes (June and July) and Insecta imagoes (August). The share of filte r-feeders Cladocera was the highest in June and amounted to 25.9% in t he class of length from 5.1 to 7.0 cm SL and 48.9% in the class of 7.1 to 9.0 cm SL. Diet overlapping was observed between rudd and roach Ru tilus rutilus (L.) in different size classes, but the high abundance o f food items suggests that competitive interactions are probably not i nfluential.