Abudefduf abdominalis
A Hawaiian reef fish that guards eggs and hybridizes with an introduced species.
The green damselfish, also called the Hawaiian sergeant major or maomao, is a non-migratory member of the Pomacentridae family. Found in the Pacific near the Hawaiian Islands, Midway Island, and Johnston Atoll, it reaches a maximum length of about 30 centimeters (12 inches). Adults prefer quiet waters with rocky bottoms in inshore and offshore reefs, from 1 to 50 meters deep, while juveniles sometimes turn up in surge pools. This benthopelagic species often forms schools and feeds on algae and zooplankton. People in Hawaii use it as food, and it occasionally appears in the aquarium trade.
Breeding occurs year-round, with peak activity from mid-December through July, depending on food availability. The fish are oviparous and polygamous, with distinct pairing during breeding. Eggs are demersal and stick to the substrate; males guard and aerate them. Males court females by taking on nuptial colors—dark blue with light yellow bars—and performing dances like zig-zag swimming, looping, or floating head down. They can hybridize with the introduced *Abudefduf vaigiensis* in Hawaiian waters.
Adults average 7 to 9 inches in length. Juveniles start with a yellow tinge that shifts to greenish white as they mature. The rear fin has a black marking. During breeding, males turn blue and their black bars fade to gray.
The diet consists mainly of zooplankton, especially copepods, with occasional algae.
Predators include the milletseed butterflyfish, raccoon butterflyfish, and black triggerfish. The milletseed butterflyfish, for instance, may follow divers to find nests and feed on the eggs.
Quick Facts
- Taxon
- Abudefduf abdominalis
Facts from the source article.
Lore & Background
Adults of the species are typically found in quiet waters with rocky bottoms in inshore and offshore reefs at depths 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. During breeding, males take on nuptial colors of dark blue with light yellow bars and perform dances such as swimming in zig-zag patterns, loops, or floating head down to attract mates. The species is polygamous during breeding, and eggs are demersal and adhere to the substrate, with males guarding and aerating the eggs. Breeding cycles depend on the availability of food. It is known to hybridise with Abudefduf vaigiensis, which has been introduced to Hawaiian coastal waters.
Reader's Guide
The green damselfish holds significance in Hawaiian waters as both a food source and a species that occasionally enters the aquarium trade. Its breeding behavior is notable: males display vivid nuptial colors and perform elaborate dances to attract mates, and they guard and aerate the demersal eggs. The species is capable of spawning year round, with peak activity from mid December through July. It hybridizes with the introduced Abudefduf vaigiensis, indicating ongoing interactions between native and introduced species. Predators include the Milletseed Butterflyfish, Racoon Butterflyfish, and Black Triggerfish; notably, the Milletseed Butterflyfish may follow divers to find and feast on the eggs of the Hawaiian Sergeant. The fish's diet consists of zooplankton (especially copepods) and algae, and its juveniles start with a yellow tinge that turns greenish white as they mature, with a black marking on the rear fin. During breeding, males turn blue and their black bars fade to gray.
Did You Know?
- The green damselfish is also known as the Hawaiian sergeant major and maomao.
- Males guard and aerate the eggs, which are demersal and adhere to the substrate.
- It hybridises with Abudefduf vaigiensis, an introduced species in Hawaiian coastal waters.
- The Milletseed Butterflyfish will travel close behind divers to find Hawaiian Sergeant nests and feast on the eggs.
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