Food relationships of the common whitefish (Coregonus lavaretus) and river perch (Perca fluviatilis) in a small forest lake

In Karelia the common whitefish biology, including its feeding, is well studied in large water bodies, but not in small lakes. We studied the peculiarities of feeding common whitefish and river perch in a small forest Lake Padashulkayarvi in the north of Karelia. It was established that these fishes use the same forage reserve, the basis of the juvenile diet is zooplankton, but grown-up individuals prefer zoobenthos. The fact that the whitefish feed mostly on shellfish and perch - on caddis flies is specific for this water body. At that, unlike other water bodies, feeding on flying insects is more typical of perch than of whitefish. Separation of trophic niches is obviously provided dynamically – by the distribution of consumed resources in space and time. Slight overlapping of the niches of the whitefish and perch is determined by the Morrisita-Horn index. Absence of acute competitive tension makes possible the coexistence of populations of whitefish and perch in a small water body.