Vertical distribution of planktivorous 0+ pikeperch, Stizostedion lucioperca (L.), in relation to particulate or filter feeding

The main prey of 0+ pikeperch in the pelagic zone of the Sulejow Reservoir was Leptodora kindtii and copepods, which together constituted only about 20% of the zooplankton by number in the water. Leptodora kindtii predominated in pikeperch food close to the surface, and copepods in deeper water. A depth-dependent shift in feeding mode from large particle selection to filtering, as an adaptation to reduce intraspecific competition and avoid predatory pressure in the upper part of the water column, was suggested. Specimens with less stomach content were observed more frequently closer to the surface. They were exposed to heavy predation from adult conspecifics, which prevented them from foraging efficiently, although they were able to feed on larger zooplankton because of better penetration by moonlight.