Diet Shift and Prey Selection of the Native European Catfish, Silurus glanis, in a Turkish Reservoir

Diet and prey selection of European catfish were studied in Menzelet Reservoir in Turkey. Diet of European catfish composed of 6 prey fish species, 1 crab (Potamon sp.) and 1 leech (Hirudo sp.). Diet composition was dominated by fish, including Alburnus kotsychyi, Capoeta angorae, Capoeta erhani, Luciobarbus pectoralis, Silurus glanis and the most important prey item was A. kotsychyi. The diet of European catfish was constituted solely by fish in winter and autumn while crab and leech contributed to a small part of the diet in spring and summer. Therefore, feeding was more heterogeneous in spring and summer than winter and autumn. The values of X2 and G statistics indicated a significant difference (P<0.05) in the seasonal proportions of prey types consumed and main source of variation comes from C. angorae in winter. Prey size did not change according to the predator size. According to the prey selection indices (V), European catfish did not show prey selectivity. A. kotsychyi was the most preferred prey, but its selection index was not statistically significant (V=-0.112, X2=2.509 and P>0.05)