THE FOOD OF PERCH (PERCA FLUVIATILIS L.) IN A BIOMANIPULATED WATER SUPPLY RESERVOIR

The food composition of perch (Perca fluviatilis, L.) was studied in a mesoeutrophic reservoir Hamry near the small town Hlinsko in the Bohemian - Moravian highlands (Czech Republic). Average depth of the reservoir is 2 m (7.5 m maximum). Fish were sampled with 100 m beach seine, fry seine and gillnets in 2011 and 2012. Food composition was evaluated using gravimetric methods. Zooplankton was dominant in 0+ (16 - 86 mm) and 1+ (52 - 81 mm) perch diet. In summer and autumn, cyprinid and perch fry dominated in adult 5-7+ (112 - 300 mm) fish while detritus dominated in spring. Benthic macroinvertebrates were recedent. While juvenile perch participate on undesirable reduction of zooplankton abundance by its feeding pressure on the other hand adult perch play an important role in fish stock management by consuming fish fry (even of its own species) that exactly feed on zooplankton and thus affects phytoplankton quantity and further the water quality.