Eurasian Ruffe (Gymnocephalus cernua)

The Eurasian ruffe (Gymnocephalus cernua), also known as ruffe or pope, is a freshwater fish found in temperate regions of Europe and northern Asia. It has been introduced into the Great Lakes of North America, reportedly with unfortunate results, as it is invasive and is reproducing faster than other species. Its common names are ambiguous – "ruffe" may refer to any local member of its genus Gymnocephalus, which as a whole is native to Eurasia.

In Aquariums and Zoos: Relativ common in european aquariums