Indo-Pacific sergeant

The Indo-Pacific sergeant (Abudefduf vaigiensis) is a type of damselfish belonging to the family Pomacentridae. It is sometimes called the Sergeant major, though that name typically refers to the similar Atlantic species Abudefduf saxatilis. Another closely related fish, Abudefduf caudobimaculatus, was once thought to be the same species and, by some experts, still is.

This fish lives across the Indo-Pacific region, including the Red Sea. In the Indian Ocean, it appears from the Red Sea and Gulf of Aden to Arabia, the Persian Gulf, the Arabian Sea, the Maldives, eastern Africa, Tanzania, Madagascar, the Seychelles, Sri Lanka, the Andaman Sea, Indonesia, Malaysia, and Australia. In the Pacific, it ranges from the Gulf of Thailand, Malaysia, Indonesia, the Philippines, Taiwan, Japan, and the Yellow Sea to the Great Barrier Reef around Australia, New Zealand, and Pacific islands as far as Hawaii. It likely entered the Mediterranean Sea through the Suez Canal, but its exact range there is unclear because it can be confused with Abudefduf saxatilis and Abudefduf troschelii.

The Indo-Pacific sergeant has a whitish-blue body with a yellow top. A black spot sits near its dorsal fin, and its eyes are yellow. Its dorsal fin has 13 spines and 11 to 14 soft rays, while the anal fin has 2 spines and 11 to 13 soft rays. The largest recorded size is 20 centimeters (7.9 inches). Juveniles mature at about 12 centimeters (4.7 inches). Males turn more blue during spawning. Many people mistake this fish for Abudefduf saxatilis, a close relative found in the Atlantic Ocean.

Its diet includes zooplankton, benthic algae, and small invertebrates. Adults inhabit coral reefs, tide pools, and rocky reefs, while larvae live in the open sea. The species is found in tropical and subtropical waters at depths of 1 to 15 meters (3.3 to 49.2 feet). These fish often form large groups, where individuals either feed in the midwater or tend their nests.

This fish appears in the aquarium trade. There have been reports of ciguatera poisoning from eating it.

Larvae hatch and drift into the pelagic zone, riding the waves until they grow large enough to settle on a reef. During breeding, males turn more bluish and build nests on rocks or coral ledges. Females lay eggs in the nests, and the male fertilizes them. He then guards and aerates the eggs until they hatch.