Most fish, but not all, have scales as a protective coating for the skin. Those scales are the remnants of the bony armor which enveloped the very earliest fishes.

1) Ctenoid scales have tiny points on their surface and are arranged in an overlapping pattern. Fish that rough to the touch, such as bass and perch, have ctenoid scales.

2) Cycloid scales are also arranged in an overlapping pattern, but have a smooth surface. They are found on such fish as carp and salmon.

3) Some primitive bony fish, including birchirs and gars, have thick, heavy Ganoid scales, which are mainly bony and covered with a kind of enamel called ganoin.

4) Sharks and most rays are covered with Placoid scales, which are made of enamel and dentine and resemble tiny, closely spaced teeth.

Some fish, including certain kinds of eels and freshwater catfish, are scaleless.

SOURCE
The World Book Encyclopedia. Chicago: World Book-Childcraft International, 1978.

Questions or comments about this page?

This page was last updated on June 18, 2017.