Food and growth of the ruff (Gymnocephalus cernuus (L.)) of the Lakhtinsky bay in Onega lake

The results of the study of ruff (Gymnocephclus cernuus (L.)) nutrition and growth in the Lakhtinsky Bay of Onega lake in the vicinity of cage trout farms are presented in the article. It has been revealed that ruffs aged 2+ to 8+ years inhabited nearby trout farming ponds. The size of the ruff was in the range of 12,0-19,2 cm and the mass of 15,3 g. to 71,3 g. Females predominated over males in a ratio of 2,8 : 1. Forage conditions for ruffs near cage trout farms in the Lakhtinsky Bay have changed over the years. In the area of cage trout farms in the oligotrophic Lakhtinsky Bay of lake Onega the growth rate of a ruff is smaller than in the mesotrophic conditions of the Kondopoga Bay of the lake. The occurrence of overweight ruffs near a cage trout farm proves its impact on ruff’s feeding regime in the Lakhtinsky Bay.