Green damselfish

Lore & Background

Adults of the species are typically found in quiet waters with rocky bottoms in inshore and offshore reefs at a depth of 1 to 50 m, although juveniles may sometimes be found in surge pools. It is a benthopelagic species, with adults known to form schools. The species feeds on a variety of algae and zooplankton, including copepods. It is known to be used as a food source for humans in Hawaii and occasionally appears in the aquarium trade.

Breeding involves distinct pairing, with males taking on nuptial colors of dark blue and light yellow bars and performing dances such as swimming in zig-zag patterns, loops, or floating head down to attract females. Eggs are demersal and adhere to the substrate, with males guarding and aerating the eggs. Breeding cycles depend on the availability of food. The species is polygamous during breeding and can hybridise with Abudefduf vaigiensis, which has been introduced to Hawaiian coastal waters.

Juveniles start out with a yellow tinge, which turns greenish white as they mature. The rear fin has a black marking. During breeding, males turn blue and their black bars fade into gray. Predators include the Milletseed Butterflyfish, Racoon Butterflyfish, and the Black Triggerfish; some predators, like the Milletseed Butterflyfish, will travel close behind divers to find a nest and feast on the eggs.

Reader's Guide

The green damselfish holds significance in Hawaiian waters as both a food source for humans and a species of interest in the aquarium trade. Its breeding behavior is notable for polygamy, distinct pairing, and elaborate male courtship dances, including zig-zag swimming and head-down floating. Males guard and aerate demersal eggs, and breeding cycles are tied to food availability. The species can spawn year round, with peak activity from mid December through July. It is also known to hybridize with the introduced Abudefduf vaigiensis, indicating ecological interactions in Hawaiian coastal reefs. Predation by butterflyfish and triggerfish, particularly on eggs, highlights its role in the reef food web. The fish's ability to form schools and inhabit depths from 1 to 50 meters, along with its presence in surge pools as juveniles, demonstrates its adaptability within its limited geographic range of the Hawaiian Islands, Midway Island, and Johnston Atoll. Its maximum size of 30 cm and average adult size of 7 to 9 inches make it a moderately sized damselfish. The species' appearance changes from yellow-tinged juveniles to greenish-white adults, with males developing blue nuptial colors during breeding. These characteristics contribute to its recognition as a distinct member of the Pomacentridae family in the Pacific.

Did You Know?

• The green damselfish is also known as the Hawaiian sergeant major and maomao.
• Males perform dances including zig-zag patterns, loops, and head-down floating to attract females.
• Some predators, like the Milletseed Butterflyfish, follow divers to find and eat the fish's eggs.