BIOLOGY OF RUFFE (GYMNOCEPHALUS-CERNUUS (L.)) - A REVIEW OF SELECTED ASPECTS FROM EUROPEAN LITERATURE

The focus of this synthesis is the ruffe research conducted in Europe during the last 100 years. Literature data about habitat, feeding ecol ogy, growth, daily ration, production, and commercial value of ruffe f rom different types of waters were compiled. In some European estuarie s, ruffe were formerly an important commercial species. Today, ruffe s till have some commercial importance in eastern European countries, e. g., Russia. Ruffe are food generalists with a tendency to feed on bent hos, but in tidal estuaries they are rather planktivorous. They have t he advantage of being able to select moving prey items under relativel y dim light or high turbidity conditions as a result of their excellen t near-field sensory resolution. Under these conditions, they are able to compete with other species for zooplankton and small fish. In the clear and less productive waters of many lakes, rivers and reservoirs, ruffe are better competitors for benthic macroinvertebrates than perc h and roach. A multivariable consumption model has been developed to a llow rough estimates of daily ration in dependence from water temperat ure and fish size. Although ruffe occur both in freshwater and brackis h habitats, they usually grow better in estuaries than in fresh water. Some authors agree that, compared to fresh water, ruffe utilize the b etter nutritional opportunities in brackish water, which ultimately in duces better growth.