Spring diet and trophic relationships between piscivorous fishes in Kaniv Reservoir (Ukraine)

Abstract

Four piscivorous fishes such as pike, Esox lucius, European catfish, Silurus glanis, pikeperch, Sander lucioperca, and Eurasian perch, Perca fluviatilis, co-occur in Kaniv Reservoir (Ukraine). In total, 47 food items were identified in their diets including remains of fish and invertebrates. Sixteen prey items were identified in pike diet including 15 fish species; 33 prey items in European catfish diet, among which 20 fish species; 21 prey items in pikeperch diet, among which 18 fish species; and 28 prey items in perch diet, among which 12 fish species. The most important prey for pike were roach, Rutilus rutilus (%IRI = 25.9 %), Prussian carp, Carassius gibelio (34.7 %), and perch (18.4 %); for catfish — roach (55.5 %) and perch (20.6 %); for pikeperch — roach (52.8 %) and perch (34.1 %); and for perch — monkey goby, Neogobius fluviatilis (85.7 %). Highest diet overlap indices were observed between catfish and pikeperch (84.8 %) while the lowest between catfish and perch (33.7 %). No significant difference was observed between the average sizes of fish prey in the stomachs of pikeperch and European catfish (t-test, P > 0.05), but there were significant differences between all other pairs of piscivorous species (t-test, P < 0.001).