Ruffe From the Former USSR: Variability Within the Largest Part of its Natural Range

Abstract

This paper reviews current data on the ruffe, Gymnocephalus cernuus L., its range, variability of its meristic and morphometric characters, diet composition and trophic relationships, habitats, behavior, growth, reproduction, and abundance. Ruffe, a monotypic species, is found from the Baltic Sea to the Kolyma River. Recent evidence extends its distribution as far as the Arctic coast both in Europe and Asia. In the south, the range is restricted by the Caucasus in Europe, and in Asia by the Aral Sea basin and upper reaches of several large Siberian rivers. Ruffe usually have a narrow home range. Their seasonal migrations are related mainly to reproduction. In lakes and reservoirs, ruffe are found everywhere from shallow to the deepest zones. In rivers, they prefer sites with slow current. Ruffe show flexible foraging, breeding, and migratory behavior. Adults compete with common bream, roach, and benthivorous whitefishes, and are the prey of pikeperch, burbot, pike, large perch, and eel. The age of maturation is similar (2 to 3 years, sometimes 1 year) from the northern to southern areas. Fecundity tends to increase from north to south. Daily specific growth rate is rather constant everywhere; the fastest growth was observed in the newly-impounded reservoirs. Ruffe variability to a larger extent depends on local ecological situations rather than on latitudinal factors. Attempts to control ruffe populations with small-mesh seines were unsuccessful and only caused a reduction in average age of populations. Introduction of some piscivorous fishes (eel, pikeperch) was more efficient.