eurasian ruffe gymnocephalus cernua detail of head

aggressive ambiguous america around back brown called cernua color common continuous distasteful dorsal downturned eurasia eurasian europe features fin fish freshwater front genus golden gymnocephalus half hard introduced invasive lakes large length likely markings member mouth names native north northern obvious olive paler pope predators rays recognize refer regions reportedly reproducing results ruffe sharp sides similar slightly soft species spines spiny temperate two undersides unfortunate usually walleye which white yellowish