Development and Food of Age-0 Eurasian Perch (Perca fluviatilis) in Reservoirs near Moscow, USSR

Eurasian perch (Perca fluviatilis) spawned in Mozhaisky and Uchinsky reservoirs in early May when water temperatures were 5–10 °C. Larvae subsisted on the yolk sac until the mouth became terminal at 6.0–7.0 mm standard length. Larval development is illustrated by drawings and discussed. As young perch grew they fed on cladocerans in preference to copepods, later switching to insect larvae. Daily ration of larvae in June was 12–16% body weight and of fingerlings 5–28% body weight, in different months and years. Most feeding was crepuscular. In the years when food was abundant fast-growing young-of-the-year matured as precocious males in autumn. They spawned with larger females the following spring. This is considered to be an adaptive response to increased food supply and low population densities. Key words: Percidae, Perca, food, development, spawning, Mozhaisky Reservoir, Uchinsky Reservoir