noun. A small spiny freshwater fish (Gymnocephalus cernuus) of the family Percidae, native to Eurasia but introduced into and spreading in the Great Lakes.

noun. undefined

noun. An obsolete form of roughie.

noun. A fish, the Eurasian ruffe (Gymnocephalus cernuus) and other species in the same genus.

"The introduction of another fish called the ruffe, which preys upon the eggs and young Gwyniads, has seen their numbers fall to as low as 31 females since the 1980s."