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Eurasian perch, Perca fluviatilis, and pikeperch, Stizostedion lucioperca, are the most widely distributed of the 11 species of percids in the USSR. This literature review examines their feeding ecology in the USSR.The pikeperch is an ambush–pursuit predator. It can become piscivorous within a few months after hatching, when it begins feeding mostly on small pelagic schooling fishes. In contrast, the perch, a facultative ambush predator, hunts during the day, eating mostly invertebrates and young fish.The daily ration of pikeperch during the most intensive feeding period constitutes 4.5–5.5% of the body weight and decreases to 0.5% during periods of less intensive feeding. The annual ration is 200–250% of its body weight. About 60% of the annual ration is consumed during spring, 15% during summer, 22% during autumn, and 3% during winter. The daily ration of perch is similar to pikeperch — 1–4% of the body weight during spring and autumn and 0.5% during other months. The annual ration of perch is 175–200% of its body weight. About 40% of the annual ration is eaten during spring, 30% during summer, 15% during autumn, and up to 20% during the winter. The conversion of wet weight of food eaten to wet weight of predator is higher for pikeperch (19.6%) and perch (18.2%) than for other predators in our area.Due to different feeding conditions the biological roles of perch and pikeperch vary even within the same water body. Adult pikeperch are always piscivorous, but perch often compete with other fishes for food and are a source of food for pikeperch and other large predators. The abundances of perch and pikeperch are inversely related; a decrease in pikeperch leads to a sharp increase in perch. In some small lakes in the forested area of northwest USSR, the fish fauna is represented by only two sizes of perch: small ones feeding on zooplankton and benthos near shore and larger ones cannibalizing the small ones; these two forms have fluctuated with 17-yr cycles.Calculation of diel, monthly, and annual rations of predators made it possible to determine the total food consumed in a year by one fish and by an entire stock of these predators. Stocking with pikeperch to control smaller fish abundance has been successful in waters with rich food supplies, but in some lakes of Middle Asia it annihilated the native fish fauna. Key words: Percidae, feeding habits, Perca, Stizostedion, annual rations

The feeding ecology of three piscivorous fish species; perch (Perca fluviatilis), pike (Esox lucius) and burbot (Lota lota), was studied in the subarctic Pasvik watercourse (69 o N), northern Norway and Russia. All three species primarily occupied the benthic habitats in the watercourse. Perch and burbot exhibited distinct ontogenetic niche shifts in food resource use; perch changing from a dominance of zooplankton to zoobenthos to fish, and burbot from zoobenthos to fish. Fish prey dominated the diet of all the investigated size-classes of pike, but small-sized pike (<20 cm) were not represented in the sample. Fish prey size was positively related to predator size in all three species. Whitefish (Coregonus lavaretus) was the dominant prey of pike and large-sized burbot and perch. Nine-spined sticklebacks (Pungitius pungitius) was also an important prey and appeared to be a dietary stepping-stone enhancing the transition from invertebrate feeding to consumption of large-sized whitefish prey for all three predators. A cluster analysis separated the different size groups of the three predator species into five functional feeding groups, most of them containing two or all three species. Within these feeding groups, and especially among the piscivorous size-classes, there was a strong and significant interspecific overlap in prey selection, and the dietary similarities between the species were in general much larger than the intraspecific similarities between ontogenetic stages. All three piscivorous species are important top predators in the aquatic food web of the watercourse, and their ontogenetic diet shifts and resource partitioning patterns generate a substantial food web complexity in this subarctic ecosystem.

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