The caudal region is the space from the end of the anal fin to the end of the caudal fin.

The caudal peduncle (tail) is the part of the body lying between the end of the anal fin and the beginning of the caudal fin.

The caudal fin is an unpaired fin which, in most fishes, acts as a propulsive organ, giving the fish forward movement. The shape of the caudal fin is semilunar (mackerel), forked (mackerel, herring), notched (carp, perch), rounded (burbot), obrean (sunfish), pointed (captain's hump). Some fish do not have it (skates). It is denoted by the Latin letter C and is an important systematic feature.

Types of caudal fins:

Heterocercal;

protocercal;

homocercal;

diphycercal.

The mechanical supporting structure of the caudal fin in fish is the skeleton. The muscles that control the fin and the fin rays are attached to the caudal fin skeleton.