Fish Scales link to an Internet Website

Most bony fish have one of two types of scales:

Cycloid scales have a smooth edge.

Ctenoid scales have a toothed edge.

Cycloid and ctenoid scales grow as the fish grows. Fish are more active and grow more in the spring and summer, causing the scales to leave rings very much like the rings of a tree. These rings are farther apart in the spring and summer and closer together in fall and winter. For this reason, the age of most fish can be fairly accurately determined by examining their scale rings.

Test your skilllink to an Internet Websitein fish age determination.
 
Ganoid scales have thick bony layers and do not form rings as they grow. These scales are found on gars and bowfins.
 

Fish Movement

Fish movement is produced by two types of body motions:

Eel-like fish, such as lampreys, move their whole body back and forth like a snake. This type of body movement produces a fairly slow motion and requires large amounts of energy.
Most fish have a firm "tail" that can be moved back and forth without moving the whole body. This type of body movement produces a fast motion and requires much less energy.

The Bony Fish