caudal peduncle

Noun

 * 1)  The narrow part of a fish's body to which the caudal or tail fin is attached. Its proportions, such as the length and breadth, and attached organs, such as spines of surgeonfishes or caudal keels and finlets of  often are important in descriptions of fish species.

Translations

 * Finnish: pyrstönvarsi
 * French: pédoncule caudal