Feeding habits of the perch (Perca fluviatilis L.) found in the river lake system of the Pista river (Republic of Karelia)

A comparative analysis of the feeding habits characteristic of the perch (Perca fluviatilis L.) inhabiting the waters of Karelian riverlake system is submitted. Significant differences in qualitative and quantitative indicators of the perch nutrition habits in the lake and river conditions of the river Pista are revealed. In conditions of the river the perch consumes multiple organisms of zooplankton. The perch’s nutrition ration, along with the typical lake victims - roach and perch includes some river species - bychek sculpin. It was found out that in river conditions the perch’s stomach fullness reaches 40 % of the initial volume. The transfer to predatory habbits is observed in perch of smaller sizes when compared to the sizes of perch feeding of lake waters. Therefore, the samples of catches and a subsequent analysis of their stomach contents showed that the ration of perch inhabiting the waters of the river Pista is very flexible. These indicators are explained by a large share of fish food (bychek sculpin, roach, perch) in the perch’s nutrition.