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green damselfishGreen damselfish
Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata
Class: Actinopterygii Order: Perciformes Family: Pomacentridae
Genus: Abedufduf Species: abdominalis
Scientific name; Abedufduf abdominalis
Common names: Hawaiian Sergeant major, Green damselfish
Hawaiian Name: Mamamo, mamo

Hawaiian sergeant majors or Green damselfish are among the most common endemic species around the Hawaiian Islands. They are colored greenish-white with five black bars that extend about half way down the body. The abdomen often develops subtle yellow striping, and their background color can lighten or darken at will. Breeding males develop a bluish hue that they can change quickly. Sergeant majors are found over rocky bottoms in shallow coastal waters. Juveniles are common in tidal pools.

Sergeant majors are commonly found swarming high above the seafloor primarily on windward sides of the reef where they feed on plankton (primarily tiny crustaceans), near to where they shelter and reproduce. When disturbed they dive for cover in unison, but soon rise again to resume feeding. In addition to plankton, these fish consume algae and small benthic creatures.

Males form colonies on the sea floor or on vertical rocks and boulders. They clear the rocks of algae in preparation for the females to lay their eggs and fight vigorously among one another to establish and hold their territories. The sergeant major males pair with multiple females but will form distinct pair bonds with each female during her laying session which reportedly lasts as long as two hours. The sergeant major males fertilize the sticky purplish eggs that females lay in their nests and then guard and aerate them until they hatch out 5-9 days later. During the nesting period, some males do not build nests but instead try and crash the party (so-¬≠called “streakers”) to fertilize the freshly laid eggs. The wealth of high-protein, high-fat food associated with these nests attracts considerable interest from all sorts of reef raiders such as butterfly fish, wrasses, surgeonfish and triggerfish. In the Turtle Reef sequence Hawaiian sergeant majors can be seen working in unison to drive off a school of Whitebar surgeonfish. At night the males abandon their nests and seek shelter leaving their nests to the depredation of crustaceans and other nocturnal species that consume eggs.

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