The yellowtail sergeant (Abudefduf notatus)[4] is a species of damselfish in the family Pomacentridae native to the Indo-Pacific.

[5] In the Pacific Ocean, it occurs in the Gulf of Thailand, Indonesia, the Great Barrier Reef around Australia, the Philippines, Taiwan, Japan, New Caledonia, and various islands in the western Pacific Ocean.

[5] Adults live in coral reefs and lagoons while juveniles are found in the open sea.

[5] Abudefduf notatus forms roving aggregations which are noted to be rather difficult to approach.

It is an oviparous species, with individuals forming distinct pairs during breeding and males guarding and aerating eggs.