Ctenoid scale is a bony scale with a serrated posterior edge (perch, ruff). It sits firmly in the skin.

From the Greek kteis - crest and eidos - kind, form.

A type of bony scale of bony fishes; the posterior margin is furnished with a ridge of denticles or spines. Characteristic mainly of perch, but is also found in some herring and cod fishes. Does not change during the life of the fish. It is assumed that the spines of Ctenoid scales improve the hydrodynamic properties of the fish body.

Ctenia are spicules invisible to the eye on the posterior pocket-free edge of the bony scales of highly organized fishes (perch, flounder).