Ruffe (Gymnocephalus cernua) is a freshwater, brackish species recorded in the United States. It is found at depths of 2–85 m.
Scientific name: Gymnocephalus cernua · Water: Freshwater, Brackish
Size: up to 29 cm
The ruffe is a benthopelagic percid that inhabits eutrophic lakes and lowland and piedmont rivers, and it is most abundant in the estuaries of large rivers, in brackish lakes with salinities up to 10 to 12 parts per thousand and in reservoirs; its abundance generally increases with increased eutrophication. It is reported to prefer still or slow-flowing water with a soft bottom and no vegetation, as well as deep water with deposits of sand and gravel, and it can tolerate some degradation of the environment. It can co-exist in deep lakes with Perca fluviatilis, the two species partly occurring at different depths with the ruffe more abundant in deeper layers. The membranous external walls of the head canals give it high directional sensitivity, and it can feed at night. Its range is Europe, in the Caspian, Black, Baltic and North Sea basins and Great Britain, north to about 69 degrees north in Scandinavia, and in Asia the Aral Sea basin and the Arctic Ocean basin eastward to the Kolyma drainage; several countries report adverse ecological impact after introduction. Maximum length is about 29 cm total length, commonly about 12 cm, and it can live ten years, maturing at about 11 cm. It is a minor commercial species, a gamefish and is usually used as bait. Fishing vulnerability is high at 59 of 100 and resilience medium. IUCN lists it as least concern.
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